| Looking for tech [message #10394] |
Tue, 03 February 2009 07:33  |
carlc
Messages: 143
Registered: July 2006
Location: Summerville, SC
|
Senior Member |
|
|
Anyone have information on a good technician in south Carolina or Denver, Colorado?
I live in SC, but going to Denver soon and need help with my 745PA head.
Thanks,
Carl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Re: Looking for tech [message #10407 is a reply to message #10394] |
Wed, 04 February 2009 11:27  |
chicagobill
Messages: 2006
Registered: April 2003
|
Senior Member |
|
|
carlc:
I don't know of any techs in either area, but if the volume problem effects both channels, I have an educated guess as to what the problem may be.
On the Frank heads, there is a electrolytic cap on the driver board that goes bad, and this will cut down the volume of the amp.
To repair it correctly, you will have to remove and remount two of the power transistors on the back panel, so it's a little involved. I don't know what your skill level is but if you want to try it yourself, let me know and I'll post details here.
|
|
|
|
|
|
|
|
|
|
|
|
| Re: Looking for tech [message #10478 is a reply to message #10475] |
Thu, 12 February 2009 14:24 |
chicagobill
Messages: 2006
Registered: April 2003
|
Senior Member |
|
|
Carl:
Yes, I was refering to C203 on the driver board.
I have four Frank heads and on three out of four of them this cap has needed replacement, so I always suggest to people that they check this cap out.
As for your amp, if this cap is ok, then without you having access to test equipment, I'm afraid don't know what to tell you to try next.
Bill
|
|
|
|
|
|
| Re: Looking for tech [message #10606 is a reply to message #10605] |
Fri, 06 March 2009 11:41 |
chicagobill
Messages: 2006
Registered: April 2003
|
Senior Member |
|
|
Carl:
The schematic that I sent to you is for all of the original K200 heads with the wide top front panel, often referred to as "Frankenstein" or "Frank" heads. The _95 designations were the model numbers of the particular amp configuration that Kustom offered at the time. So if your amp has the wide top front panel, then yes, it's the right schematic for your amp.
The cap I suggested to check is located on the small PC board bolted down to the inside back panel. When you have the front of the amp towards you, the board will be on the left side of the back panel. There are two large transistors that are connected to this board, one is the voltage regulator for the pre-amps and the second one is the driver transistor for the output stage.
The reverb board on your amp will be mounted vertically and parallel to the left side wall of the chassis.
Bill
|
|
|
|
|
|
| Re: Looking for tech [message #10609 is a reply to message #10608] |
Fri, 06 March 2009 18:11 |
chicagobill
Messages: 2006
Registered: April 2003
|
Senior Member |
|
|
Carl:
The three important things to know are the capacitance value, the voltage rating and the case type.
As you noted it is a 500uF cap. If you can't find a 500, a 470uF would be fine there too. The voltage rating should be a minimum of 35 volts. The case type here is an axial type, meaning the leads come out of each of the ends of the case. If your local sources don't have one, Mouser will have them.
To test it out, you can temporarily clip the new cap in parallel with the old one to see if fixes your problem. With the amp off, either tack solder the new cap to the leads of the original one or use a couple of alligator clip leads. As these caps are polarized, be sure to hook up the positive to the positive and the negative to the negative. The new cap could explode if you hook it up backwards.
Carefully turn on the amp and see if the amp's volume is back to normal. If it is, then you should remove the old cap and replace it correctly with the new one. Once you get to this point, I'll give you more instructions, but for now you can see if that cap is the problem.
Bill
|
|
|
|
VintageKustom.com
Search
Help
Members
Register
Login
Home
]