Amplifier Corporation of America - Fuzz King [schematic]

[jrod]

interesting. franke's schematic mentions (note at top) that the actual transistors are RCA 2n2613. that is a germanium pnp part. would probably sound a lot different with the si trans listed on the schematic at the trans symbols.

there are so many weird rare 60s fuzzes, i wish i had a lot of them just for fun.

Not sure why he has a different transistor listed by Q1, 2, & 3 on the schematic, but if you look at the top he has written, "Transistors all RCA 2613".

[IamJon]

Guys,
I know this thread has been dead for a while.
I actually have the exact one that is pictured on discofreq's site; down to the scratches, jacks, etc. I got it a couple of years back. As for the 4.5V battery, I think it came with one when I got it but I will have to dig through my stuff to find out. I must have put a 3.6V LiSO4 battery in it as it was the same form factor (AA). I have never been able to get it to sound worth while. It has almost no output. If anybody has any suggestions on how to make it sound good or verification of components/schematic, I would be happy to share that info. If it is supposed to have positive ground, that would be good to know because as it stands, the battery is in the holder with negative ground. Also if it is really supposed to use a 1.5V AA, that may also help.

[IamJon]

OK then.
After reviewing various pnp fuzz schematics I see that I have the battery reversed. I hope the thing isn't fried. Also to note the battery is LiSOCl2 not LiSO4.

[IamJon]

Ha... well the battery wasn't reversed but the coupling/blocking electrolytic cap on the lower left had no signal passing through it - hence no output. When I acquired the thing, the seller indicated it was "as is" and that they didn't know if it worked because they couldn't test it. Someone may have been trying to read the component values and tugged and twisted too hard on one of the leads on the cap. I found the battery that came with it. Eveready Energizer NO. 333 NEDA 1306 4 1/2 Volts. It is the same length as an AA but slightly larger diameter.

[chriscolt]

I recently received an original Fuzz King for Repair. I have corrected the schematics that have been posted to this website and will try to post it. The problem with this unit was no audio output - what I found was a bad electrolytic (one of the 1 uf/25V caps) so I changed both since electrolytics tend to go bad with age. In addition, the circuit board (which warps with age) is screwed down to the metal chassis, the screws also act as grounding lugs to the chassis (this is a Germanium PNP positive grounded system - 1.5 Volts). The underside of the board indicated solder points and component leads hanging off the bottom of the board by around 1/16" to 1/8". Depending on how tightly the mounting screws for the board are screwed down - this may cause a short between those solder points and the chassis - this is EXACTLY what was causing the problems with this pedal (still didn't work after 1 uf cap was changed - even though cap was definitely bad - "opened") - as soon as the board was detached from the chassis and lifted an inch - the problems went away.

I created an insulating board of paper/cardboard and heavy clear plastic sheet - the cardboard faces the board and the plastic faces the chassis the two materials are sandwiched together and holes made for the mounting screws to keep it in place under the board. Screwed it all back together and viola - problem gone. Troubleshooting this unit took some time (thought bad cap was the problem, then checked transistors with Heathkit IT-18 transistor tester, resistors with VOM, Caps with CAP analyzer, then traced circuit and put in signal from Ipod to input, used cheap analog telephone headset to trace signal point to point using schematic to trace signal failure - no signal detected after 1st resistor in circuit even though all components tested correctly).

Apparently the short only affected the "signal" and not the DC control voltage flowing through components. New schematic is correct - added pullup resistor (R12- 220K) for Q3 to reduce gating of Q3 (improved sustain and better Fuzz / Clean sound and wider range of Fuzz control). Transistor Voltage readings are actual (using 3 x RCA 2N2613 Ge PNP) reading taken with new 1.5AA alkaline battery and with and without 220K pullup resistor added to original circuit - see schematic

Thanks hope this helps
Chris

[LucifersTrip]

Thanx alot for posting all the info. I checked my build notes and when I built one, I made changes nearly identical to your correction.

Though, there's a couple important measurements you left out that'd be killer to have. Since you used the Heathkit tester, you must've removed the transistors. hfe & leakage?

Those would be cool, but have been reported by others in similar fuzzes, though one measurement I'd love to see hasn't.
The range of Q2C voltage as the fuzz pot changes?

With the common fuzz/bias control from Q2B to ground like in the FZ-1, Q2C voltage can change from a little under 1.5 down to .6 - .8v, and some people noted above and below that. For the FZ-1A,it's pretty easy to pick a Q2, but with the Fuzz King's fuzz control, I found it tougher.

You can pick something that makes the whole thing sound good, only to find out that the Fuzz pot does little or nothing. Think about it...you already have a large resistor (1M) across B/C and you have to choose a Q such that a very little proportional change (100K) makes a a big change from no fuzz to max fuzz. I believe that if Q2 has too much leakage, Q2C voltage will be too low (too much fuzz) to start and changing the pot will do little. So you can't get away with as much leakage as in the FZ-1A. In mine, Q2C went from around 1.3V down to around .8V.

I had that problem when repairing an LRE Fuzz, which is almost identical.



When I got it, there was barely any fuzz...just a low volume gating (Both Q2 & Q3 C were right around 1.5V). To make a long story short, I had to remove & replace Q2 & Q3. I made no other replacements to get it to work. My initial Q2 choice gave good fuzz, but the Fuzz pot did little or nothing. The odd thing was that Q2 and Q3 were good transistors...both had around 60 hfe with low leakage (<100uA), so I had to guess that the thing never worked, since transistors don't get better with age...

Also, with these FZ-1 variants, I usually find Q3C to be a little lower than what you had to start, and closer to what you got with R12. Most I've built (and originals) are usually in the 1 - 1.2V range and one was 1.3V.

Anyway, thanx again for posting.

[modman]

1966 unit:

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1968 unit:

1968-amplifier-corp-of-a-fuzz-king-gre-7rp0uUj.jpg (37.82 KiB) Viewed 3346 times

1968-amplifier-corp-of-a-fuzz-king-gre-8fH54pa.jpg (39.54 KiB) Viewed 3346 times