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New to me K200B-1 [message #20136]

Fri, 14 February 2014 13:33

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Came across this on CL so drove 100 miles to go get it.

http://i1197.photobucket.com/albums/aa426/rehernden/Mobile%20Uploads/0214141125_0001_zpsc7b063b8.jpg

Sounds nice except for the hiss. Been reading the forum here for the past couple days and will try some of the "fixes" to see if I can quiet it down a little bit. Previous owner has already done the three prong power cord, and replaced the speakers with Eminence Delta 15-B's. Speaker jack is labeled Jensen.

First I'll try de-soldering the blue wires at driver board to try to isolate where hiss is coming from. Also there is a pulsating hum on the normal side. Could this maybe be the big filter caps?

I'm no electronic tech but reasonably confident I can de-solder and replace transistors etc if I can determine which ones need it. Trying to figure out the different part numbers is a little confusing. Has anyone considered making some "sticky" posts with FAQ's and maybe a clear part # cross reference and where they are located on schematic for newbies such as myself?

Anyway, thanks for a great site I would be totally lost without it.

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Re: New to me K200B-1 [message #20137 is a reply to message #20136]

Fri, 14 February 2014 15:37

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Welcome to the place! Congrats on the new addition to the family. It looks like it is in very nice shape.

Hum in one channel only will probably not be a main filter cap, as they supply the entire amp. Could be as simple as a bad ground connection.

Again congrats and welcome.

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Re: New to me K200B-1 [message #20138 is a reply to message #20137]

Fri, 14 February 2014 19:09

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

Congrats on the amp and cab. Photo looks like it's in nice shape. Can't help you much on the hum, but when the speakers were replaced, they may not have ordered 16 speakers as replacements. If they are 8 ohms you would have a 2.6 ohm total load to the head. The K200 amps want a 4 ohm total load for the full rated output. Going below the 4 ohm may damage the amp.

pleat

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Re: New to me K200B-1 [message #20139 is a reply to message #20138]

Fri, 14 February 2014 20:10

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Yea, I was a little concerned about the ohm rating. After looking on the Eminence website the Delta 15-B only showed 16ohm. Cannot find a rating on the actual speakers. Previous owner had them wired parallel but the top speaker went thru a capacitor or resistor that looks factory. I guess the Jensen's that were in there had a different horn or something in the top position? I bypassed that and just have them standard parallel for 5.33ohm. Thanks for the welcome, will probably have some other questions along the way.

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Re: New to me K200B-1 [message #20140 is a reply to message #20136]

Fri, 14 February 2014 22:12

sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota

Senior Member

Love it! it looks bad ass even with out the ports!!!!

-S

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Re: New to me K200B-1 [message #20144 is a reply to message #20136]

Sat, 15 February 2014 03:36

Kustom_Bart
Messages: 601
Registered: October 2010
Location: Greenville, MichiGUN

Senior Member

Is the capacitor about as big around as your thumb and about 2 1/2-3" long? if so then it was meant for a siren horn as the crossover and used to be a siren cabinet. It would of had 2 15" speakers in the bottom two holes and then a spun aluminum horn in the top hole. They work great for PA mains set up that way. I have a pair with Altec speakers in them.

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Re: New to me K200B-1 [message #20148 is a reply to message #20144]

Sat, 15 February 2014 09:29

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Maybe not quite that big, should have written down the number. This is before I bypassed it.

http://i1197.photobucket.com/albums/aa426/rehernden/Mobile%20Uploads/0210141200_zpsecd674f9.jpg

Here's one of the speakers, couldn't find any ohm rating on them so have to trust their website. They sound good.

http://i1197.photobucket.com/albums/aa426/rehernden/Mobile%20Uploads/0210141200a_zps1d977ea0.jpg

On another note. I read that some people replace the filter caps with 10,000uf 50v but may have to upgrade the bridge rectifier also. Would it make sense to just put in a couple 6500uf 50v and not have to change bridge rectifier. Not sure I need to do this yet but just thinking ahead a little.

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Re: New to me K200B-1 [message #20151 is a reply to message #20148]

Sat, 15 February 2014 21:31

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Had a chance to play thru this rig today. sounds nice, everything works, don't notice the hiss when playing. When pushed kinda hard, guitar volume about 80 percent, amp volume at 1:00, plucking low a, e, or g notes pretty hard the bottom speaker farts a bit. can't really blame that on the amp. These speakers sell for $100 each so maybe that's all they can handle. Normally don't play that loud so no worry's and having second thoughts about replacing any transistors etc. Now just need to get a coiled cord for the complete 70's vibe. Cool

Cool

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Re: New to me K200B-1 [message #20152 is a reply to message #20136]

Sun, 16 February 2014 08:34

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

If you want the best sound from that amp if you are playing bass
You really need to get ports into the cabinet!!
In stock form the 3-15 cabinets are far two small for 3-15s, (heck the 2-15 cabs are border line to small) to sound there best even with the stock size ports.
For those delta 15b`s are looking for 7.20 cubic ft of cabinet volume each.
In short those cabinets need a minimum of 4 stock size ports, with at least two it will fart out less on the low E string.
Oh,sorry I forgot,welcome to the place!

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Re: New to me K200B-1 [message #20153 is a reply to message #20152]

Sun, 16 February 2014 09:23

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Hmm, didn't think about that. It has four 2 1/2" ports behind the grill cloth already. Wouldn't be hard too make four more and give it a try. Thanks for that idea.

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Re: New to me K200B-1 [message #20154 is a reply to message #20136]

Sun, 16 February 2014 09:33

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

You need to have tubes behind them even if they do not pass out thru the grill cloth.
Parts express sells kits to make up the lenght tubes you need.
Another option is to make slot type ports on the bottom and top of the baffel.

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Re: New to me K200B-1 [message #20155 is a reply to message #20154]

Sun, 16 February 2014 10:33

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Wow! There's a lot of math and science involved to determine port size, location, and tube length. Apparently it is easy to make matters worse is done incorrectly. I'll have to find an online calculator and study this a little bit.

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Re: New to me K200B-1 [message #20156 is a reply to message #20155]

Sun, 16 February 2014 12:16

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

All good points on the port tubes and such, but it won't make a kustom cab sound like a new computer designed cab. From what I've read, your using the system for guitar. One thing you may want to try first is to make sure that the baffle board is bolted tightly to the cabinet. Over time the nuts may have worked loose. I'd also make sure that each speaker, the nuts are snug evenly. Since you mentioned only the bottom speaker is farting out, it may be the speaker is not evenly secure to the baffle board. On cabinets I've boughten over the years that the grill cloth is dusty or drinks spilled on them. I remove the baffle board, head to the car wash and power wash and rinse them. Vacuum off the excess water, and let them dry in the sun for a hour or so. Brings the grill cloth to factory fresh and allows me to make sure all nuts are secure when I reassemble the cab.
pleat

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Re: New to me K200B-1 [message #20157 is a reply to message #20155]

Sun, 16 February 2014 12:28

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Found a simple online port length calculator so I won't have to do any math. I don't like math.

http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%2 0Port%20lenth%201.htm

According to this calculator I need 2.19" for 45hz for the four ports that are already there. 6.21"-45hz if I put four more ports. Of course it changes with different hz. This is for 2.5" dia ports.

Does this sound about right? 45hz seems to be inline with the eminence speakers.

I use this for bass guitar. The grill cloth was kinda dusty, cleaned it up best I could but the car wash idea would be better. I checked all the nuts when the back was off and they were tight. Wonder if the baffle board is really needed with these different speakers.

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Re: New to me K200B-1 [message #20158 is a reply to message #20136]

Mon, 17 February 2014 01:43

Kustom_Bart
Messages: 601
Registered: October 2010
Location: Greenville, MichiGUN

Senior Member

s far as the bridge rectifier, do not mess with a Kustom amp unless it is giving you problems. They are not amps that you dive into and just start replacing parts unless they need it. This amp will last a very long time as you will never turn it up loud enough to hurt the head, you will hurt yourself first....lol! They are the opposite of tube amps that you have to piddle with all the time.

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Re: New to me K200B-1 [message #20160 is a reply to message #20158]

Mon, 17 February 2014 08:23

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Yea, volume at 12:00 seems to be plenty. Haven't decided yet if I'm going to replace any transistors to remove some of the white noise, really it is no louder than the fan on my SWR sm400s head. Will probably experiment on the cabinet some to see if I can get rid of the bottom speaker distortion since it's no longer "original" with the new speakers.

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Re: New to me K200B-1 [message #20161 is a reply to message #20136]

Mon, 17 February 2014 08:33

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

The first transistor after the input jacks on each preamp board would be the place to start as the noise from these transistors gets amped up hundreds if times by the gain stages on down stream.
With a cost of some 50 cents for two of them you can scrape that up from your cars under seat area!

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Re: New to me K200B-1 [message #20162 is a reply to message #20161]

Mon, 17 February 2014 09:04

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Laughing

That's funny, I'm gonna go out right now and check my car. Thanks. I read one of your other post's about the first three transistors. Gonna practice on an old circuit board first then may give it a try for real.

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Re: New to me K200B-1 [message #20165 is a reply to message #20160]

Mon, 17 February 2014 11:59

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

I'd move the bottom speaker that is causing some issues to the top position and the top speaker to the bottom. If the issue stays in the bottom position, then you have some cabinet issues. If the issue follows the speaker, then you have a speaker that will need to repaired.
pleat

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Re: New to me K200B-1 [message #20166 is a reply to message #20165]

Mon, 17 February 2014 12:29

Kustom_Bart
Messages: 601
Registered: October 2010
Location: Greenville, MichiGUN

Senior Member

I agree with Pleat 100%. It may be a speaker problem and not a cabinet problem.

My dad owned a service station and wrecker service for 35 years and you would be amazed what I would find under the seats of wrecked cars. I began working there when I was 10 or so years old. When he hauled in a wreck we were liable to clean out any personal property, so that was my job, I would box it up for the owners to pick up. Then I got to search the car under the seats etc, after it was turned over to us. I have found everything from diamond rings to condoms....lol! once a 100 dollar bill too. LOL! However, it was nothing to find 6.00 or more in change under the rear seat.

[Updated on: Mon, 17 February 2014 12:30]

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Re: New to me K200B-1 [message #20167 is a reply to message #20166]

Mon, 17 February 2014 12:38

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

I'm gonna take your advice pleat and move the speakers first, I hope I would have thought of that on my own before doing anything else but who knows.

As for loose change. I do remember find some every so often under the cushion in my dads recliner back in the 60's. Good times.

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Re: New to me K200B-1 [message #20244 is a reply to message #20167]

Tue, 04 March 2014 11:18

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

After closer exam discovered all three eminence speakers are suffering from over excursion. Took the back off so I could see what they were doing and made it worse of course.
So as an experiment I made some block off plates for the port holes and it helped a little but since these delta 15-b speakers only have 1.6mm xmax they just can't seem to handle the power this amp puts out. Found some other speakers with twice the xmax but just one would cost almost as much as I paid for this whole rig.

As for the amp. Went ahead and bought some new transistors but could not bring myself to cut the two blue wires to see where the white noise is coming from. Only original once except for the replacement 3 prong power cord so guess I'll live with the hiss for now. Don't know if keeping the circuit boards original will help resale value years from now or not.

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Re: New to me K200B-1 [message #20253 is a reply to message #20136]

Wed, 05 March 2014 07:19

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

The 100 watts of rms power from the amp should not drive even just one of those speakers to xmax unless those drivers had been in a different cabinet for sub use and drivin to death!

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Re: New to me K200B-1 [message #20255 is a reply to message #20253]

Wed, 05 March 2014 08:55

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Yea that's what I thought too since they are rated at 400 watts each but I think that is what's happening. They sound like little hammers when push to hard, from what I've read that's what over excursion sounds like. Also tried putting some port tubes on tuned to 40hz with no change. Maybe you're right and they have been abused in the past some time, they sound great otherwise.

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Re: New to me K200B-1 [message #20261 is a reply to message #20255]

Thu, 06 March 2014 19:10

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

Have you tried the amp with a different speaker cabinet or the kustom cabinet with a different amp head to see if the problem stays with the cab or follows the amp head?
pleat

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Re: New to me K200B-1 [message #20262 is a reply to message #20261]

Thu, 06 March 2014 20:35

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

I have a 4x10 4ohm cab I'll try it with and a another amp to try with the kustom cab to see how it goes.

In the meantime I went ahead and cut the two blue wires with no change in the white noise which I guess means it is coming from the power amp. So changed the four 36892 transistors mounted in a row on the bottom of amp with 2n3055's location Q1-Q4 on the schematic I think. Pretty easy with no soldering, put some new heat sink compound on and it seems to have reduced the noise by maybe a third, not very scientific but it does seem a little quieter. Everything I've read so far says there will always be some white noise so not sure about trying anything else or not.

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Re: New to me K200B-1 [message #20263 is a reply to message #20136]

Fri, 07 March 2014 06:35

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

Kustom used 4 matched outputs for low crossover distortion levels, if your amp now sounds like its got a horrible distortion to it when played up near its full RMS power level thats why.
If thats the case you can swap those 4 new ones around from place to place and see if it gets better.

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Re: New to me K200B-1 [message #20264 is a reply to message #20263]

Fri, 07 March 2014 09:19

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

steven. Are these 4 matched outputs the 2n3055's I just put in or something else?

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Re: New to me K200B-1 [message #20266 is a reply to message #20136]

Fri, 07 March 2014 11:59

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

They may be the same part number but that's no guaranty that they will all pull the same idle current , or have the same gain so to speak.
Play it loud and give it a listen, you will hear if it's got nasty distortion or not compared to what it sounded like with the original outputs.

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Re: New to me K200B-1 [message #20268 is a reply to message #20266]

Fri, 07 March 2014 13:44

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Okay gotcha.

Tried my SWR amp with the kustom cab and it sounds about the same, so I don't know. Can dial back the bass and it's not as bad and probably shouldn't be playing that loud anyway, but get carried away sometimes Smile

Smile

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Re: New to me K200B-1 [message #20281 is a reply to message #20136]

Sat, 08 March 2014 08:40

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

If you hook up a new 9 volt battery across each driver and the cone moves in or out more than 1/16" or so then the drivers need to be reconded.

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Re: New to me K200B-1 [message #20282 is a reply to message #20281]

Sat, 08 March 2014 09:02

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Thank you, I will try that.

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Re: New to me K200B-1 [message #20352 is a reply to message #20282]

Thu, 20 March 2014 16:40

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Finally got around to testing the speakers with 9 volt battery. They move somewhere between 1/16" and 1/8" kinda hard to judge the distance but doesn't look like more than 1/8". While in there removed the port block off plates and put port tubes back on tuned to 38hz if my calculations are correct. Really can't tell any difference in overall sound with or without the tubes in place. It is louder though without the plates on there.

Now that the white noise is isolated to the power amp (by cutting blue wires) would it make since to replace the transistors located at Q1-Q4? Is it really possible to remove all the white noise from these amps?

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Re: New to me K200B-1 [message #20353 is a reply to message #20136]

Thu, 20 March 2014 17:14

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

I'm not sure I know which transistors you are referring to so I don't have an answer for you on that one. The hiss can be caused by transistors or resistors or capacitors. Each case is different. The hiss is generated more in earlier stages of the amp where the gain factor is large and less in the final output stage where the gain is less.

You can make these amps quieter, but all amps will have some background hum and hiss. How loud is it compared to your other amps?

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Re: New to me K200B-1 [message #20354 is a reply to message #20353]

Thu, 20 March 2014 20:29

rehernden
Messages: 20
Registered: February 2014
Location: Blairsville, Ga

Junior Member

Sorry, I take that back about Q1-Q4 I think those are the transistors mounted on the bottom of chassis and I have done those but remember there being 6 of them. Reading the schematics is a bit over my head.

The hiss is really not all that bad, is more than my Carvin PB500 which is nearly silent, but less than the cooling fan on my SWR SM400s, this SWR used to have a pretty bad hiss but had a tech fix it with a new signal path whatever that is. If I stood further away the Kustom probably would not notice it so much.

I don't mean to draw this thread out too long and appreciate everyone's input. I may have come across a k300 pa amp and cabs and may have some questions about that if I end up with it.

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Re: New to me K200B-1 [message #20355 is a reply to message #20136]

Fri, 21 March 2014 01:11

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

The 4 large transistors on the bottom are the output transistors. On a K200B there should be 4 on an aluminum extrusion that also has the bias diode and the thermal cutoff switch connected to it.

There are two additional large transistors on the power amp board that are part of the low voltage regulator circuit.

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