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K 300 [message #18950]

Sun, 07 July 2013 21:07

mrg2u
Messages: 34
Registered: July 2013

Member

I have a Kustom 300 P.A. head and I can not get any sound out of it. everything inside looks good, caps are not swollen, nothing seems burnt,. i can not find any thing listed as 300. Is this similar to other models and can I use a different schematic to check it out. The main problem is the power switch. the wiring on this i white, white w/a black stripe and red. i can not find any such colors on any of the schematics I have found. It did work until the switch went bad. Thanks in advance for any help.

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Re: K 300 [message #18952 is a reply to message #18950]

Mon, 08 July 2013 09:54

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

How did your switch fail? did it the plastic snap where the hold down nut mates to the metal bracket?
If so you can use two cable ties, one on each side of the switch shaft to pull and hold the swtich back up to the inner side of the metal bracket.
I do this to all my amps for the metal face serise that use this type switch even if they are not busted yet as this will prevent the brakage from taking place.

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Re: K 300 [message #18953 is a reply to message #18952]

Mon, 08 July 2013 11:31

mrg2u
Messages: 34
Registered: July 2013

Member

one of the metal arms fell out. ZI saw your cable tie idea and it did not work for me. I do believe the only problem is getting the wires routed correctly but I can't find anything on the schematics that show a red wire involved w/ the switch and no green wire at all.

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Re: K 300 [message #18954 is a reply to message #18950]

Mon, 08 July 2013 11:57

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

I believe that the red wire you are talking about is for the pilot lamp inside the switch. The white and white with black stripe are the ac power wires.

If you look at the polarity switch there will probably be a green wire added there for its' pilot lamp.

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Re: K 300 [message #18956 is a reply to message #18954]

Mon, 08 July 2013 14:30

mrg2u
Messages: 34
Registered: July 2013

Member

Yes , there is a green on the polarity switch, so then switching the white and white/ black should power it up but it goes not. Although I am not an amp tech, I have had a lot of experience w other electronic systems and I can't figure why I am not getting any sound. You can hear the power being drawn through the stero speakers which are in the same room. A distinct pop when this should be powered up but no sound.

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Re: K 300 [message #18957 is a reply to message #18956]

Mon, 08 July 2013 15:17

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

mrg2u wrote on Mon, 08 July 2013 13:30

A distinct pop when this should be powered up but no sound.

Do either of the pilot lamps in the two front switches light up? If you are hearing the amp power up, then the lights should light up unless both lamps are burned out.

If you have electronics experience, try using a voltmeter to read the power supply voltages at the filter caps and see if you have plus and minus 40 volts.

If the voltages are there, then try and send a signal directly into the power amps to see if they are working.

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Re: K 300 [message #18958 is a reply to message #18957]

Mon, 08 July 2013 15:31

mrg2u
Messages: 34
Registered: July 2013

Member

Caps read good. Going to see if I get anything out of the power amp.

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Re: K 300 [message #18959 is a reply to message #18958]

Mon, 08 July 2013 15:42

mrg2u
Messages: 34
Registered: July 2013

Member

O.K. Now I am confused. Power amp is the board on the bottom of th unit.? Correct.? Blue , red, green coming off the capacitor side and black , orange pink on the other side which all three have infinity to ground. ????

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Re: K 300 [message #18960 is a reply to message #18959]

Mon, 08 July 2013 15:48

mrg2u
Messages: 34
Registered: July 2013

Member

o.k. , so black .orange. pink are the return grounds from the output jacks, where do i get straight in to the power amp.?

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Re: K 300 [message #18961 is a reply to message #18959]

Mon, 08 July 2013 15:51

mrg2u
Messages: 34
Registered: July 2013

Member

o.k. , so black .orange. pink are the return grounds from the output jacks, where do i get straight in to the power amp.?

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Re: K 300 [message #18962 is a reply to message #18950]

Mon, 08 July 2013 16:48

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

The power amp board should be marked PC5029. The input hot is an orange wire that comes from the mixer-reverb board. Black is ground, Blue wire is speaker output and the pink wire is the tape/monitor output.

Do not unhook the black ground wire during testing. I can't remember if the input of the power amp is capacitor coupled or not, so be careful with whatever you use to inject a signal into the power amp.

When you were testing power supplies, did you test the plus and minus 12 volts preamp supplies as well?

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Re: K 300 [message #18963 is a reply to message #18950]

Mon, 08 July 2013 17:30

mrg2u
Messages: 34
Registered: July 2013

Member

I do have sound there, it is weak though, clear but low volume w/a guitar going to it.

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Re: K 300 [message #18964 is a reply to message #18950]

Mon, 08 July 2013 17:41

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Did you test the 12 volt supplies?

Put everything back to normal and turn up the master reverb control. Shake the reverb tank, does it make any sound through the speakers?

Keep working forward through the circuits to find out where the signal stops.

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Re: K 300 [message #18965 is a reply to message #18964]

Mon, 08 July 2013 18:00

mrg2u
Messages: 34
Registered: July 2013

Member

Nothing on the reverb but don't I need a footswitch to turn that on./

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Re: K 300 [message #18966 is a reply to message #18965]

Mon, 08 July 2013 18:05

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

Senior Member

No switch needed to turn the reverb on. It is on all the time the pedal turns it off. You can turn it off by turning it down.

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Re: K 300 [message #18967 is a reply to message #18966]

Mon, 08 July 2013 18:23

mrg2u
Messages: 34
Registered: July 2013

Member

Nada on the reverb tank. I cleaned the crown connections and no go.

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Re: K 300 [message #18968 is a reply to message #18967]

Mon, 08 July 2013 18:44

mrg2u
Messages: 34
Registered: July 2013

Member

can i bypass the reverb tank by placing a crown across the 2 terminals on the board./

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Re: K 300 [message #18969 is a reply to message #18950]

Mon, 08 July 2013 22:05

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Why are you trying to bypass the reverb tank? Try pulling the RCA plug from the tank output and then with the amp on and the reverb turned up touch the tip contact. If the circuit is working you should hear a buzz, just like when you touch the tip of a guitar cord plugged into the front of the amp.

If there is no buzz or no reverb, then there is no output from the mixer board. Again check the low voltage power supplies and check the output chips on the mixer board.

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Re: K 300 [message #18970 is a reply to message #18969]

Tue, 09 July 2013 00:03

mrg2u
Messages: 34
Registered: July 2013

Member

seemed like the next step but I will check the output. This is learn as you go for me.

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Re: K 300 [message #18971 is a reply to message #18950]

Tue, 09 July 2013 07:16

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

You need to have the master reverb control up also to get any reverb out of the 6 channels.

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Re: K 300 [message #18972 is a reply to message #18971]

Tue, 09 July 2013 08:44

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

Senior Member

Since the K300 uses the Molex connector plugs from board to board, I think I'd try cleaning the connectors and make sure everything is making a good connection. I've had kustom amps given to me that were considered dead. Quick cleaning of the connectors the amp comes back to life.
pleat

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Re: K 300 [message #18973 is a reply to message #18972]

Tue, 09 July 2013 11:03

mrg2u
Messages: 34
Registered: July 2013

Member

i get nothing on the reverb tank either shaking it or touching the positive on the out put. In looking at the man control board, inputs and volume controls, I am not finding power anywhere and on the main power amp, i have no power on the left hand side either. I have power to the switches both the main power and the polarity switch but after that i find none. I also cleaned all the connections before i started as I had seen that post before.

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Re: K 300 [message #18974 is a reply to message #18950]

Tue, 09 July 2013 12:15

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Please explain in more detail, as I don't understand what you are saying about the missing power.

Did you get correct dc voltages at the two main filter caps of plus and minus 40 volts dc?

Do you have the correct low dc voltages for the preamps of plus and minus 12 volts dc?

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Re: K 300 [message #18975 is a reply to message #18974]

Tue, 09 July 2013 13:23

mrg2u
Messages: 34
Registered: July 2013

Member

yes I do get both. where it disappears is on the left 3 resistors on the power amp and beyond the polarity switch on the control boards. I am absolutely sure that i am missing something stupid here so i have a friend w/ more knowledge coming by to take a look . He and I will go back through the checks you have given me and see if he comes up w/the same thing I am,.I really appreciate all the help but like I say, I believe I am missing something critical in all of this.

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Re: K 300 [message #18976 is a reply to message #18975]

Tue, 09 July 2013 22:32

mrg2u
Messages: 34
Registered: July 2013

Member

well, some progress anyway. The bridge rectifier has a crispy, intermittent resistor in it and so there is power to the control board and then not. Seems that is why it would work and then not work, depending on how it was moved as a whole so, tomorrow I will go and get all 4 new resistors and put them in. Hopefully this will solve the problem but if not, at least I will have power there and be able to trace further down the line. I will let you know how it turns out.

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Re: K 300 [message #18977 is a reply to message #18950]

Wed, 10 July 2013 13:11

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

I'm glad that you found some sort of problem. Hopefully that will fix it right up.

If the amp is original, the only bridge rectifier that I know of in the amp is mounted directly to the chassis. It connects directly to two of the wires from the power transformer. Is this what you are talking about?

It is made up of 4 diodes not resistors, so be sure that you get the right parts as replacements.

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Re: K 300 [message #18978 is a reply to message #18950]

Wed, 10 July 2013 18:30

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

The only dropping resistors in these amps stock off of the rectifier bridge are the ones that are bolted down to standoffs on the chassis floor.

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Re: K 300 [message #18979 is a reply to message #18978]

Wed, 10 July 2013 22:06

mrg2u
Messages: 34
Registered: July 2013

Member

Resistors on the chassis it s, i am mixing my metaphors, it is a long story . Any way, that is where the control board is losing power so even if there is something else wrong it will be easier to trace down w/the power on. could not get these at Radio Shack so it is online to Mouser. Couple of days to get them and I will let you all know the result. I really like the way this thang sounds so I will keep on it till it lives again.

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Re: K 300 [message #19067 is a reply to message #18979]

Fri, 09 August 2013 18:15

mrg2u
Messages: 34
Registered: July 2013

Member

i finally got my resistors.!1 I am dying to put them in and see if this cures it but I have to go pick the wife up at the airport and that will probably turn into dinner, which I don't mind , so , look for an update sometime tomorrow.

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Re: K 300 [message #19239 is a reply to message #19067]

Mon, 26 August 2013 22:32

mrg2u
Messages: 34
Registered: July 2013

Member

Well, finally got a chance to put the resistors in and still no sound. i can surely here the power side kicking on or off and I can hear the cabinet speakers hissing w/power on but.... the other thing happening is the 150 K resistors are both getting very hot which would explain the toasted one I found. Now it will be a matter of finding out what it is in the input board that is causing that and as you know, 6 channels w/12 inputs, that is where the most component parts are to sift through. wish me luck and if there is any advice out there i would certainly appreciate it and thank you in advance.

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Re: K 300 [message #19240 is a reply to message #19239]

Mon, 26 August 2013 22:52

mrg2u
Messages: 34
Registered: July 2013

Member

One more bit of new info. I tried moving the lock plunger on the reverb tank to see if I got any twang and what I get is super loud pops and static, like full volume pops. Hmmmm.

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Re: K 300 [message #19242 is a reply to message #18950]

Tue, 27 August 2013 06:39

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Those loud pops with the tank unlocked means that the tank has one or more of its two springs broken, so add a tank to your list for parts now.
In regards to the signal problem, now that you have the new resistors in place are you getting the + and - 12 volts into any of the preamp boards, or is it getting loaded down to less than 12 volts.
Do nothing more untill you get back to us with what you have voltage wise,

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Re: K 300 [message #19244 is a reply to message #18950]

Tue, 27 August 2013 11:53

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

And I hope that the resistors you replaced are 10 watt, 150 ohm and not 150K.

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Re: K 300 [message #19245 is a reply to message #18950]

Wed, 28 August 2013 06:36

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Yea bill I hope so also, but atleast if they are above 150 ohms no harm will come to the amp.

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Re: K 300 [message #19256 is a reply to message #19245]

Fri, 30 August 2013 12:14

mrg2u
Messages: 34
Registered: July 2013

Member

I got the resistors from mouser and they are exact replacements. i opened the reverb tank and the springs and coils all look good and solid.???? I will check the voltages and get back to you. yhanks guys.

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Re: K 300 [message #19263 is a reply to message #18950]

Fri, 30 August 2013 15:08

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Does the reverb lock work? all of these I have ever seen by now Have the foam gone on the face of the round plate due to dry rot.

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Re: K 300 [message #19269 is a reply to message #18950]

Fri, 30 August 2013 19:17

mrg2u
Messages: 34
Registered: July 2013

Member

The foam is still there but the lock portion on the shaft is worn off...no lock.

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Re: K 300 [message #19414 is a reply to message #19269]

Wed, 25 September 2013 18:37

mrg2u
Messages: 34
Registered: July 2013

Member

O.k. So things have been insane here and I am just getting back to this. The resistors are an exact match, 2 ea, 150 ohm and 2 ea. 400 ohm, same as what came out. I do get the + - 12 on the boards but the volume, w/a guitar plugged in is very low. The reverb tank springs are in tact and have continuity through them. If you move the reverb springs you get a very loud static sound and as I am probing for voltages I get the same loud pops when the meter lead contacts the test point.

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Re: K 300 [message #19416 is a reply to message #18950]

Thu, 26 September 2013 12:09

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

It sounds like the power amp and the mixer boards are working to some degree. Have you tried all of the individual pre-amp channels? Are they all low in volume?

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Re: K 300 [message #19420 is a reply to message #18950]

Thu, 26 September 2013 18:24

mrg2u
Messages: 34
Registered: July 2013

Member

Yes, all across the board, low .

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