 K100B-5 [message #25801] |
Fri, 27 January 2017 13:03  |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Hi Members! I'm new here, but not to using Kustoms. I had (still have) my K200 bass amp with 3x15 that I bought new in 1971. I still use it today when I play. Although at 60, it ain't so easy to cart around anymore.....
So, here's my deal. I've been collecting Kustoms for a while. When I bought the ones I have, they all worked. They stayed in a basement for a long time, and now, well, they don't work. Since I'm now disabled I thought I would learn about electronics and possibly repair the units myself. I can read schematics fairly well, and can solder like a banshee, so I am going to try the first one soon.
This one is a PA head, K100B-5. I know for a fact that the transformer is fried. Didn't even have to test it. Plugged it up and heard wonderful bubbling and sparking sounds coming from the transformer. Immediately unplugged it.
So, these transformer puppies aren't so easy to find. At least not through conventional means. I see a lot of used out there, none tested of course...., but haven't managed to find the one I need yet.
Identification numbers are:
019-7002-01
1005827.
Got any ideas?
Thanks folks,
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25803 is a reply to message #25801] |
Fri, 27 January 2017 20:27  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Welcome to the place.
Original transformers are difficult to come by unless they come out of another head. The good news is, normally these transformers are pretty much bulletproof. In all the years that I have worked on these amps, yours' is only the second one that I've seen go bad.
So, you can put a classified ad here and see if any of the guys here have a K100 head that they are parting out or you can search eBay for one. Alternatively you could have the dead one rewound or you could try and find a generic replacement from Edcor or Hammond.
I will dig out the one K100 chassis that I have and see if it still has the power transformer.
As for fixing these amps, they are really basic designs and are very simple to fix. You can post questions here and we can help you to get the collection back up and running.
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| Re: K100B-5 [message #25805 is a reply to message #25803] |
Fri, 27 January 2017 22:48 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Thanks Chicagobill. That would be an immense help! I figured this was the head to start with as it's the most expendable of the ones I have. The other 5 I fully intend to either use or sell in the near future. So yes, I would appreciate the help! Let me know if you have the t-former.
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25806 is a reply to message #25801] |
Sat, 28 January 2017 06:26 |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Hello and welcome to the joint/ place!
Don't fret I have a list of new Toridal type transformers for all vintage Kustom amps but the Metal face PA 600 model.
These will provide a tad more current and better performance then the originals , I just do not have my info here at work so I will have to post back to you later in the day.
These Toridal types mount with one bolt down thru there center, so you will need to drill atleast one new hole to mount them either on the floor of the amp or the rear wall.
Another option is to stand them up by using a L bracket to support them on each side, but then your drilling atleast 4 new holes.
To connect it to the round rectifier bridge you will need to crimp on new Female spade ends or just Solder it to the bridge.
In regards to the rectifier bridge and seing as your original PT is toast I would check it out also as it may be shorted out also.
If you need to know how to test the bridge out just post back, but the thing is it's been under a lot of load and may infact be what did in your PT in the first.
If it was not what did in your PT then the amp has shorted out semiconductors in the output stage that will need to be tested out and replaced first before even firing up the amp with the new PT in the first place!
If you go to the repairing Kustom amps section and go into the first posting titled Help you read where we have been helping out a fellow with his amp and learn how to prove out your amps output stage even before you get the new PT in hand.
[Updated on: Sat, 28 January 2017 06:30] Report message to a moderator |
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| Re: K100B-5 [message #25817 is a reply to message #25801] |
Sun, 29 January 2017 17:14 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I had a chance to pull out the chassis and it does have the transformer and bridge rectifier. A quick test gave me plus and minus 42 volts dc. No signs of hum or mechanical buzz.
It will need to be cleaned up a little. If you are interested, PM me and we'll wheel and deal.
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| Re: K100B-5 [message #25826 is a reply to message #25805] |
Mon, 30 January 2017 10:56 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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HI Steve,
Thanks for your suggestions and helping me get started here. You guys make this a great place. I believe I will be getting the T-former from Chicagobill, as we'd already talked about it and he has gone to the trouble of pulling it out. The other suggestion you had was a great one and I will start checking that out today. I hope you folks don't get bored with me asking really dumb questions, but I promise my learning curve is quick.
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25828 is a reply to message #25826] |
Mon, 30 January 2017 11:43 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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The power transformer could have been damaged by any number of things, too much current, too much moisture, etc. You need to test things in order to try and figure out why it happened and how to keep it from happening again.
The very first thing to check is the ac power fuse. On the K100 amps the fuse is soldered into a fuse holder located on the back wall of the chassis. It should be a 3 amp fast blow fuse. I've seen them replaced with 20 amp car fuses or jumpered across with wire. Without the correct fuse, the entire amp is unprotected from damage.
The first thing that the power transformer connects to is the bridge rectifier. This is just four individual diodes mounted in a single package. The two purple wires from the power transformer connect to the two AC input terminals. The other two terminals are the + and - DC voltage outputs. The red wire is + positive and the green wire is - negative, referenced to the chassis ground.
After the bridge rectifier, the next stage is the main filter capacitors. These are the two large cans mounted to the bottom of the chassis. There are two screw terminals on top of each cap, one is positive and the other is negative. The red wire from the rectifier will connect to the positive terminal of one cap and the green wire will connect to the negative terminal of the second cap. The purpose of the filter caps is to remove or filter out the 60 hertz ripple from the DC voltage supply. Thus the name filter caps. After the filter caps, the dc voltages are sent off to the different stages of the amp.
You already know that the transformer is cooked, but check the fuse, the bridge rectifier and the two main filter caps for shorts.
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| Re: K100B-5 [message #25831 is a reply to message #25827] |
Mon, 30 January 2017 12:33 |
chicagobill
Messages: 2006
Registered: April 2003
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Steve, I just looked up those numbers and I don't think that either will work as replacements for K200B heads. The Avel Lindberg is is rated at 40/40 volts ac which would rectify to plus and minus 56 volts dc. The Triad is rated 40 vct which would rectify to plus and minus 28 volts dc.
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| Re: K100B-5 [message #25834 is a reply to message #25801] |
Mon, 30 January 2017 13:35 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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K100B-5
I just tested the bridge rectifier and both of the large can capacitors using BOTH a digital Klein MM330 and an old analog dial type meter.
Tested all wires first, all ok.
Rectifier:
On the diode setting
Positive lead tested 1.972 on the right power lead, and 1.978 on the left power lead.
Negative lead tested .0 on both power leads.
Capacitors:
On left, 0.0 reading that climbed to 72,7 then dropped to 0
On right 0,0 climbed to .05 and dropped to zero.
Meter setting on 200
R&L refer to looking front to back.
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25836 is a reply to message #25834] |
Mon, 30 January 2017 14:41 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Okay lets start with the rectifier. Set your Klein meter to the diode test function. If the rectifier is original to the amp, it will look like a small hockey puck with four terminals. If you look carefully, two of the terminals are marked AC and the other two are marked + (pos) and - (neg).
Touch and hold the red meter lead to the terminal marked - (neg). Now touch the black meter lead to one of the AC terminals. You should see some sort of reading on the meter, somewhere about .6-.7 volts. Next touch the black lead to the other AC terminal. Again you should get a meter reading of about .6-.7 volts. Next reverse the meter connections and hold the black lead to the neg terminal and touch the red lead to the two AC terminals. The meter should not show any reading at all just like when the two leads are not touching anything.
Test the second side of the rectifier by touching and holding the black lead to the pos terminal and touching the red lead to the AC terminals. With this configuration you should get the .6-.7 volt readings from both AC terminals and again no readings or open when you reverse the two meter leads.
To quick test the two filter caps, set your meter to read resistance. Set it to the 2K scale. Touch and hold the black lead to the neg terminal of one of the filter caps. Now touch and hold the red lead to the pos terminal. If the cap is good, you may or not get a reading or it will read very low and then slowly rise to infinity. Next reverse the two meter leads and you should get a very low reading that slowly rises to infinity.
If either reading stays low or at some non infinite reading it may be bad. You should then retest the cap after removing all of the wires connected to one of the two screw terminals.
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| Re: K100B-5 [message #25842 is a reply to message #25836] |
Wed, 01 February 2017 14:06 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Hi Bill,
First, your help is so appreciated. I typed all this in yesterday, but when I hit post, it all disappeared. SO, trying again today.
RECTIFIER:
Negative Side
Red lead on Neg: post 1--- .493 post 2---.493 ///// REVERSED Blk on Neg: post 1---- 1.978 and drops to 0 post 2---- 1.946 and drops to 0
Positive Side
Red lead on Positive: post 1--- 0 slow climb to 1.978 and drops to 0 ///// REVERSED Blk on Positive: post 1--- .501 and constant post 2---- .502 and constant
CAPACITORS:
LEFT CAP
WIRES OFF:
Black to Neg -9.34 climbs to 0 STOP
Black to Pos .04 climbs to 0 STOP
---------------------------------------
WIRES ON:
Red to Neg .04 drop to 0 STOP
Red to Pos .67 drops to 0 STOP
============================
RIGHT CAP
WIRES OFF:
Black to Neg 0 slow climb to 1.987 then drops to 0
Black to Pos -.02 climbs to .497 STOP -- constant
---------------------------------------
WIRES ON:
Red to Neg -.369 slow climb to 1.995 drops to 0
Red to Pos 0 slow climb to 1.988 drops to 0
NOW, THE BIG NEWS: You mentioned checking the fuse. I did. Just like you said, someone used an automobile fuse in there. BUSS 30. A 30 amp fuse. No wonder it's fried. I just hope the damage doesn't go too far into it.
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25843 is a reply to message #25801] |
Wed, 01 February 2017 16:49 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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From your numbers, I'd say that your rectifier is good and the filter caps do not appear to be shorted.
I'm not surprised with the fuse replacement, I've seen worse.
A point regarding your readings. When you say it drops to 0, do you actually mean that it rises until it gives the same meter indication as when the two meter leads are not touching anything? Or does it actually lower in value until the meter indicated the same as when the two meter leads are directly touching together? This is a very important point for us to communicate clearly as there is a huge difference between a dead short and an open connection.
If you plan to fix a few different amps, you might want to at this point look into building yourself a light bulb limiter. It will help you to troubleshoot your amp and to save you from having to replace dead fuses and new parts while you investigate the problems.
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| Re: K100B-5 [message #25844 is a reply to message #25843] |
Thu, 02 February 2017 11:51 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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The numbers climb slowly and when they hit the highs mentioned, it drops instantly. As if you touched the two leads together during an OHM test. There is no slow or gradual drop.
Would one of the Radio Shack test probes work for the test light?
Keep On Truckin'
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| Re: K100B-5 [message #25845 is a reply to message #25844] |
Thu, 02 February 2017 11:56 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Removing the old transformer today, unless you advise different and will install the other one when I receive it. PM me regarding either Paypal or address. Thanks.
Keep On Truckin'
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| Re: K100B-5 [message #25846 is a reply to message #25801] |
Thu, 02 February 2017 12:43 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I still think that we are not clear with some of the meter readings, but we will burn that bridge when we get there.
The light bulb limiter that I suggested is basically a 60-100 watt incandescent light bulb wired in series with the ac power line of the amp under test. When the amp draws too much current the light bulb lights up and takes up all of the current draw, keeping the amp from burning up and it keeps the fuse from blowing as well. If the amp is not drawing too much current, the light bulb does not illuminate and the amp will usually power up and work pretty much as normal.
If you Google light bulb limiter, you will probably find a number of sites that have complete instructions on how to build one. You don't have to have one, but if you are new to this and are planning to do a few amp repairs in the future, it will make your life a lot easier. In the shop I work at, every amp repair that comes in starts by being plugged into a limiter to see that it is not blowing fuses. That way we are not doing any additional damage to the amp and we can save a lot on the costs of test fuses.
If you remove your dead transformer, you might want to think about changing the ac power cord to a three wire grounded one at the same time, as it will be easier to do all at once. If you decide to do that we can give you instructions on how to do that as well.
As for losing your typing, I've had that happen too. The system seems to time out and basically logs you out if the post takes too much time to type in. I usually just highlight all of the text and copy it into the buffer so that if it logs me out, I can just login and paste all of the copy into a new post.
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| Re: K100B-5 [message #25847 is a reply to message #25846] |
Thu, 02 February 2017 12:54 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Yessir. The test light will be assembled and installed today. I had thought changing to a grounded power supply cord might be a good idea. Headed out to get proper fuses and such today, t-former removed. Thanks.
Later: Have supplies and will build current limiter (pm'ed you a video). Have New cord as well.
Keep On Truckin'
[Updated on: Thu, 02 February 2017 15:05] Report message to a moderator |
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| Re: K100B-5 [message #25848 is a reply to message #25847] |
Thu, 02 February 2017 17:22 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Just solder the new white lead to the same spot that the original white wire was connected and the new black wire to the same spot that the original black wire was.
When you replace the power cord, you should remove the ground cap from the power switch and use that ground connection on the chassis for the green ground wire of the new cord.
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| Re: K100B-5 [message #25878 is a reply to message #25848] |
Tue, 07 February 2017 14:54 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Received transformer this morning. Remittance in the mail. Thank you.
New grounded power cord installed per instructions.
Current limiter assembled and ready.
Transformer installed and complete.
Ready to plug in, or no?
Richard
Keep On Truckin'
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| Re: K100B-5 [message #25879 is a reply to message #25801] |
Tue, 07 February 2017 20:59 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Start by disconnecting the amplifier circuit from the power supply. At the top of the two filter caps remove the red and green wires that connect to the power amp board. There should be only the red and green wires from the rectifier going to the filter caps and of course the ground connections.
Plug the amp into the limiter and plug the limiter into the wall. Time for the smoke test. Turn on the amp and watch the light bulb. It should briefly light up and then dim down to almost off. If it stays bright there is a problem with the power supply and you will need to test a few things. If the bulb dims, then you can read the voltages at the filter caps. You should get about 45 volts dc on each of the caps. Read to ground, the red wire will be positive and the green wire will be negative.
If you get that far, then the next step will be to test the two output transistors.
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| Re: K100B-5 [message #25880 is a reply to message #25879] |
Wed, 08 February 2017 14:25 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Well, the bulb stayed bright. Both switch directions. For grins, I measured voltage with power engaged, and the left cap measured o.o, and the right 36.7--both measured from ground.
Keep On Truckin'
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| Re: K100B-5 [message #25881 is a reply to message #25801] |
Wed, 08 February 2017 15:18 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Which cap reads zero, the green negative side?
For the time being, disconnect the wire that connects the zero voltage cap to the rectifier. Now turn it on and see if the light bulb lights up. If it doesn't, the cap is bad. If it still lights up the rectifier is bad.
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| Re: K100B-5 [message #25883 is a reply to message #25801] |
Wed, 08 February 2017 15:57 |
chicagobill
Messages: 2006
Registered: April 2003
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You can replace the cap with another Computer Grade screw terminal cap or you can go with a Snap-In solder terminal cap. The Snap-In will be much cheaper.
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| Re: K100B-5 [message #25885 is a reply to message #25801] |
Wed, 08 February 2017 18:02 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Mouser Electronics has both types. A quick check show that the CG screw terminal cap costs about $29.00 and a snap-in one costs about $4.00.
The CG will probably fit right into the existing capacitor clamp. The snap-in will be about 1/2 the size of the original, so the clamps will need to be replaced or an adapter ring will have to be constructed.
The snap-in cap has solder terminals so the existing wires will have to have the screw terminals removed and soldered to the cap.
Personally, I use the snap-in caps and in your case I would replace both of the caps with new ones rated at 4700uF @ 50 volts, which is almost double the original value.
When I fix one of these amps for others, I build a small pc board that has two 10-32 screw terminals just like the original cap has that solders onto the new cap, that way the old wiring can be used as is.
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| Re: K100B-5 [message #25889 is a reply to message #25801] |
Fri, 10 February 2017 21:33 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Do you have any 50 volt capacitors around? If you do, you can substitute it for the bad one to see if the power supply will power up normally. The value really doesn't matter for this test.
Also you can test the two power transistors that are mounted to the bottom of the chassis. Pull off the black plastic plug with the yellow and blue wires and use the diode test function on your meter. The pin where the blue wire connects is the Base, the pin with the yellow wire is the Emitter and the case mounting screw with the red wire is the Collector.
Touch and hold the red meter lead to the Base pin. Touch the black lead to the Emitter pin and note the reading. Next touch the black lead to the red case Collector screw and note the reading. Then reverse the two meter leads and note the readings.
The final test is to touch and hold the red lead to the Collector and the black lead to the Emitter pin. Note the meter reading. Then reverse the two meter leads and note the meter reading.
In no case should you get a zero reading (just like holding the two meter leads together). In one direction you will probably get a reading of about .6 volts and reversed, open circuit (just like when the two meter leads are not touching anything).
Post your readings here and we'll review.
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| Re: K100B-5 [message #25892 is a reply to message #25889] |
Sat, 11 February 2017 11:18 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Thanks. Pulled plugs, readings are consistent as follows:
Transistor #1 (left)
.554
.545 / 0L
0L / 0L
Transistor #2 (right)
.559
.555 / 0L
0L / 0L
Each test is shown in the order you mentioned, and the diagonal separates when the probes were reversed. The 0L reading is the normal reading on this meter when no tests are being performed. It also show on these tests.
Also, I did not have additional caps available to do the power up test.
Keep On Truckin'
[Updated on: Sat, 11 February 2017 11:27] Report message to a moderator |
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| Re: K100B-5 [message #25893 is a reply to message #25801] |
Sat, 11 February 2017 11:39 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Good test results, both transistors seem to be fine. It may be that the filter cap is the only thing that was causing your problem. Well that and the oversized fuse.
The last thing to check is the thermal compensation diode that is mounted to the heatsink. Carefully check to see that the two wire leads are intact and that they are soldered securely to the board. The leads on these diodes will often break off at the point where they are glued into the metal case and are difficult to replace, so be gentle when handling them.
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| Re: K100B-5 [message #25897 is a reply to message #25894] |
Sun, 12 February 2017 07:27 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Caps arrived late Saturday. Installing today. If no precautions I will move forward. I believe the red mark on the old caps indicates the positive + side.
Keep On Truckin'
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| Re: K100B-5 [message #25898 is a reply to message #25897] |
Sun, 12 February 2017 12:11 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Installed the caps and new seats wiring exactly as removed. Disconnected wires to amp and performed light test. No light on the bulb at all. Tested voltage with Klein meter on 200 V and got 90.7 on each. Discharged caps and awaiting your reply.
Keep On Truckin'
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| Re: K100B-5 [message #25899 is a reply to message #25801] |
Sun, 12 February 2017 14:32 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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No light up of the light bulb is a good sign. Not sure how you tested that voltage, your 90 volts is double what it should be.
Meter set to 200 volts dc scale? Black lead connected to the chassis? Red lead to the terminal with red wire from the rectifier? Red lead to the other cap with the green wire from the rectifier?
The red wire terminal should be about +45 vdc and the green terminal -45 vdc.
Check these readings and if you get the correct plus and minus voltages, discharge the two caps and then reconnect the rest of the circuitry. With no speaker plugged into the amp turn it on and see what the light bulb does.
If you don't get the correct voltages, let me know and we'll go through the power supply wiring.
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| Re: K100B-5 [message #25900 is a reply to message #25899] |
Sun, 12 February 2017 19:07 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Ok. My bad. Hence the name Greenpea at the start of this thread. Wrong meter settings.
I got +41.7. And -41.4 respectively.
Discharged and reconnected the removed wiring. Turned it on.. Light stays off.
Keep On Truckin'
[Updated on: Sun, 12 February 2017 19:11] Report message to a moderator |
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| Re: K100B-5 [message #25901 is a reply to message #25801] |
Sun, 12 February 2017 19:17 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Well next step is to turn it on with the speaker connected and see if the bulb stays dim and if the amp passes signal.
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| Re: K100B-5 [message #25903 is a reply to message #25901] |
Mon, 13 February 2017 12:17 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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We have signal.
Lamp out while testing.
All 4 channels working, but pots are very dirty so I will work on those today.
#4 channel gives an audible popping sound, and the signal appears weaker.
Reverb is not working on any channel. Possibly I connected it wrong. Used a foot switch to no avail.
Keep On Truckin'
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| Re: K100B-5 [message #25904 is a reply to message #25801] |
Mon, 13 February 2017 13:01 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Great to hear. Start by cleaning all of the pots. I suggest using DeoxIt brand cleaner, it's the best that I've used.
The reverb only turns off with the footswitch, so don't use one for now. The first thing to do is to test the reverb tank itself. Disconnect the reverb tank wires from the pc board side. Set your meter to read resistance, use the 2,000 ohms scale. Read the resistance across the ends of the RCA plugs. You should get a reading of about 180 ohms or so on both plugs.
If you get OL readings on either end, check to be sure that the cables are making good contact. If one or both sides still read open, you'll have to remove the black foam rubber cover from the open side of the tank to inspect the small wires that connect the transducer coils to the RCA jacks. These wires often break from flexing. If you find any broken ones, resolder them and test the resistances again. Once you know that the tank is okay, plug it back in and retest the reverb function of the amp.
Channel 4 may get better after the amp has been on for a while. See what happens after cleaning the pots and testing the reverb tank.
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| Re: K100B-5 [message #25905 is a reply to message #25904] |
Mon, 13 February 2017 13:07 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Will do. Man, the hiss and hum is pretty loud! Will post results in a bit.
Keep On Truckin'
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| Re: K100B-5 [message #25906 is a reply to message #25905] |
Mon, 13 February 2017 13:31 |
irish77060
Messages: 49
Registered: January 2017
Location: Atlanta, GA
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Member |
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Channel 4 has settled down a good bit. No noises of dirt/corrosion in the pots now.
Got correct readings on reverb plugs. .178
Inspected wires inside tank, all is as should be. All springs intact as well.
Not sure if I mixed up the input & output wires. So I reversed them. Black wire grounded to chassis. Still no reverb on any of the channels.
Keep On Truckin'
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