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Do I actually have a Frankenstein?? [message #21276] Tue, 26 August 2014 09:55 Go to next message
Jerrybass1955 is currently offline  Jerrybass1955
Messages: 45
Registered: August 2014
Location: NC
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I have been working on the tremolo and reverb issues with my K100-2 and as I dig in, I am finding some unusual things.
Like:
Significant numbers of resistor values not the same as either Rev. 3 or Rev. 4 schematics. I have found three in the reverb circuit and haven't really looked much elsewhere. None of the resistors look like obvious replacements. R162 was 33K, R165 was 150 ohms and R170 was 100 ohms (instead of 15K!).

I found an extra part - a 100K resistor that may be connected to the reverb input to ground. Maybe there are more!

Transistor locations are slightly different than the transistor location map would suggest.

Serial number is 33804
PCB says "KEI-1 PC104"

Thought I had a rev. 4, but not so sure now. What do you think? Anyone know what I have?

If it is a Frankie, is there any documentation out there that might be useful? Suggested modifications?

Any suggestions on whether I should update the values to match the Rev. 4 schematic? (already did some of that in the reverb circuit with somewhat positive results - e.g., changed R 170 from 100 ohms to 15K!)

Jerry
Re: Do I actually have a Frankenstein?? [message #21277 is a reply to message #21276] Tue, 26 August 2014 10:30 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4728
Registered: June 2004
Location: NY
Senior Member
I do not know about the resistors as I will need to do some research, but Term Frank heads refers to the first series of K200 heads before the A series of heads, The K 100 amps came to be about the same time the K200 A amps where coming into production .

[Updated on: Tue, 26 August 2014 10:31]

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Re: Do I actually have a Frankenstein?? [message #21279 is a reply to message #21276] Tue, 26 August 2014 11:56 Go to previous messageGo to next message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
The Frankenstein or Frankie terms come from the shape of the head cabinet of the earliest K200 amps. In order to have a space to mount the reverb tank, the top section of the front panel was made wider than the side panels, so when looking at the front of the amp it had a tall forehead just like the imagery of the Frankenstein monster.

During this time period the model numbers were all based upon the brand of speaker and the list price of the amp/speaker and what features the amp had. So a model C595 would have no fx and CTS speakers. A model C695RV would have Reverb and Vibrato with CTS speakers, etc. Because all of the prices ended with 95 these amps are sometimes referred to as 95 series amps. When the K200A series amps were introduced, there were too many different models to continue using the list price as the model number, so a new numbering system started. Unfortunately the 95 numbers were kept for the PA heads, so there are some 95 PA amps that are not Frank circuits, but are early A-series circuits. These amps are easily recognized by the lack of the tall forehead case.

As for your K100 questions, your amp is a different version than either the ver. 3 or 4. So if it is an earlier version you can go through the amp and convert it to a ver.4 or you can just try and fix it as is. I don't own any K100s and other than basic tech info, I have no real insight to help guide you.

[Updated on: Tue, 26 August 2014 11:58]

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Re: Do I actually have a Frankenstein?? [message #21282 is a reply to message #21279] Tue, 26 August 2014 17:57 Go to previous messageGo to next message
Jerrybass1955 is currently offline  Jerrybass1955
Messages: 45
Registered: August 2014
Location: NC
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Thanks guys. Consider my question more generic in nature - perhaps a Frankenstein by another name. Smile

Looks like it is similar to both the rev. 3 and 4, but clearly different when you start looking closely at the parts. First thing that jumped out at me was that 100 ohm resistor where a 15K is supposed to be. I figured if that value had drifted downward the signal to the pot would be higher. Once I found the resistor and realized it really was that 100 ohm resistor, I figured replacing it with 15K would tame the reverb a bit - and it did help, but more taming to be done. Then I started looking elsewhere and started finding these other little Easter eggs! It gets more interesting!

Oh yea, forgot to mention, I have been seeing reference to transistors with built in or clip on heat sinks. I have none in this amp. Should I worry? Replace the drivers with something beefier?

Jerry
Re: Do I actually have a Frankenstein?? [message #21283 is a reply to message #21282] Tue, 26 August 2014 18:06 Go to previous messageGo to next message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
Q127 and Q128 are the drivers in your amp. What transistors are currently installed?
Re: Do I actually have a Frankenstein?? [message #21287 is a reply to message #21276] Wed, 27 August 2014 09:00 Go to previous messageGo to next message
Jerrybass1955 is currently offline  Jerrybass1955
Messages: 45
Registered: August 2014
Location: NC
Member
Q127 is RCA 38869
Q128 is RCA 38870
Neither has a heat sink - just metal can.

Three other metal cans are on the board too - no heat sink.

Q123 is RCA 38134 (or 38734?)
Q126 and Q119 are RCA 38735

I think I saw replacement crosses for these somewhere but can's seem to find them now. I know these are Kustom numbers but not sure of the actual RCA numbers. Got that handy?

Jerry
Re: Do I actually have a Frankenstein?? [message #21290 is a reply to message #21287] Wed, 27 August 2014 12:28 Go to previous message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
Those numbers are correct per the schematic. There is a note on the schematic that states that the two driver transistors should have clip on heat sinks. Your amp may have been built before that was added by the factory.

I'll have to look for any cross references to those numbers and add them to the list.
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