| Schematic needed.... [message #7153] |
Sun, 09 July 2006 07:23  |
carlc
Messages: 143
Registered: July 2006
Location: Summerville, SC
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Hi all,
I'm new to the board. I have a Kustom that I bought new in '65 or '66. I've lost power and am in need of a schematic for repair.
It is a 745PA, reverb on one channel. Red sparkle with a dual 12" cabinet.
Thanks for the help!
Carl
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| Re: Schematic needed.... [message #7172 is a reply to message #7170] |
Mon, 10 July 2006 15:17  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Welcome to the board Carl.
As most of the folks here know, I love the high brow K-200's, and having fixed all of mine, I'll tell you where to look first.
If I understand it correctly, your amp powers on, but you have no power? If so, then first check the large cap on the small driver board that is located on the back panel. It is cap number C203 on the schematic that Steve will send you. It is a 500mf electrolytic cap. Depending upon how old your amp is, it probably is a black plastic cylinder, about 1/2 inch in diameter and 2 inches long. If this cap opens up or drifts too low in value, it will cutoff the driver transistor and your amp will lose power or not make any sound at all. To replace it correctly you will need to un-mount the board by removing the two attached power transistors. If this is too much for your skill level, either refer service to a qualified pro, or just clip the leads off the cap and solder the new one to the old leads above the board. Not too pretty but it will get the job done. I prefer undoing the transistors, as this allows me to clean and re-grease them. Remember that this cap is polarized and must be installed in the right direction, or it may blow up (literally!).
As long as you are at it, you'll find another one of these same caps on the reverb board on the left side of your amp as well. It too should be replaced, as it has also probably drifted out of spec as well.
Best of luck,
Bill
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| Re: Schematic needed.... [message #7175 is a reply to message #7173] |
Mon, 10 July 2006 18:06 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Carl:
You should go ahead and re-mount all of the output devices while you're in there. Removing the back perforated panel will probably take the most time.
When you get into it, you'll find that the Frankenstein heads have a ground loop problem in the reverb tank circuit, that causes a hum. If your tank is original, both RCA jacks are grounded to the metal tank. Both of the cables also have grounded shields causing a ground loop. If you unhook the ground on the drive cable you should find that the hum will drop quite a bit. I believe that the factory tried to fix this by attaching the short ground wire that connects the metal reverb tank with the amp chassis, which actually made the problem worse.
Also, with the way that the tank is mounted inside the top of the case, I don't know if the cardboard encasement will work.
Bill
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| Re: Schematic needed.... [message #7271 is a reply to message #7270] |
Wed, 09 August 2006 11:44 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Carl:
Don't ya just hate it when life gets in the way of one's hobbies!
There could be a few different reasons for the wrong color on your id tag. But, if you've owned it since it was new and it has never been out of your hands, then a factory error is probably the explanation. It's not difficult to switch cases and if your dealer needed a red head to go with red cab, then he may have made the switch.
I remember reading a few posts here, about Bud Ross telling stories about the old days when factory repairs may have really been exchanges. Or at least that's what I remember.
Keep us posted on your progress.
Bill
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| Re: Schematic needed.... [message #7701 is a reply to message #7689] |
Wed, 11 October 2006 11:20 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Carl:
Congrats on getting it up and running again. There is still a lot of life left in these old amps.
A question for you... I don't own a Frank-PA, and I know this has been asked before, but I can't remember if it was ever answered: Are the 0.005 "HIGH" input caps removed from the PA heads? I know that the front panels are not marked high and low, and I would assume that they are not installed on a PA, but maybe you could let me know for sure.
Just wonderin'
Bill
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| Re: Schematic needed.... [message #7712 is a reply to message #7153] |
Thu, 12 October 2006 14:48 |
carlc
Messages: 143
Registered: July 2006
Location: Summerville, SC
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Senior Member |
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Bill,
Don't know for sure. I took a bunch of pictures of the inside while I had it apart, but none that show those inputs.
Figures, thought I had a good idea with the pics and after it's all buttoned up I'd like to take a few more.
Carl
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