Vintage Electro-harmonix Clone theory. NOISY! Help?

[anticpunk]

Hey,

So my latest aquisition is a vintage Clone Theory based on the SAD1024. This thing is so noisy that you can barely make out the chorus effect. I'm wondering if anyone has deleted the internal x-former in favor of a wall-wart with these pedals before and what effects it had if any on the performance of the pedal. I'm most positive it is the source of the noise.

It has it's own rectifier setup and LM7815 on board, so removing the transformer and rectifier and replacing that with a DC Jack seems pretty straight ahead. Maybe a charge pump and then run it on 9v?

Also is there a NOS source for SAD1024s anywhere? I know there are long OOP, but I'm wondering if there might be an issue there (although you can hear a chorus effect in the static and hum it's just drowned by them).

Thanks,

Jay

[Lee_ranaldo]

Change all electrolitic capacitors. Old Caps tends to produce a NOISY SOUND in the audio path.. too much hiss

Some ground loops make the interla powered EH stuff into a complete motorboating unit. i fix this just turning around the plug on the wall wart to resolve this. This doesn't happen when you don't use the ground terminal of the plug.

My reissue mistress has a inside transformer with no artifacts at all
the only mod i did to improve the sound of it is to change the caps for green polyester film caps (as you can see in old japanese boss pedals).

a Charge pump will do the job fine, there is a DIY project for the clone theory that already uses it.

Almost all BBD based effects has a internal trimpot to set the "BIAS" or operation point of the circuit.
there must be another for the clock or delay trimpot  try to locate that trim pot and adjust it (after you changed all the old electrolitics) to make the sound of the chorus fuller with no distortion at all.

SAD1024 are OOP but still replaceable with MN3007, with some mods on the clock circuit

Good Luck!

[anticpunk]

hey,

Thanks for the reply!

I did the charge pump and it runs off of 9vdc no problem now. Great mod in my opinion, but it's still noisy. Will start swapping caps as time permits.

I got the original EH schematic for the Sad1024 based Clone Theory from a guy who used to work for them. shows the proper setting for the trim pots (there are 3 of them). Will tweak after re-capping.

-Jay

[smccusker]

hi, i have the same problem with my vintage EH hot tubes which i still havent been able to pin down. A word of caution, when desoldering any components, be extremely careful because the circuit board traces can lift very easily, and then you have all sorts of problems. take it from me, i know first hand 

good luck with the solving the problem though!

[anticpunk]

Recapping didn't fix the HotTubes? Is it possible that, after so many years, the onboard voltage regualtor might be causing leakage or noise/spiking that could cause some of these issues? Also, if your unit is AC, I wonder if adding a true full-wave bridge rectifier in the line would be better filtering than the 2 diodes EH relied upon back then. If you can make the voltage you need from a charger pump, I would suggest that also. Using the 'pump I get 17.89Vdc from a 9.17Vdc supply which is then regulated by my 7815. runs right off of the daisy chain that way.

The supply may not be either of our issues, but might be worth modifying while we're at it.

I think I will have time to Re-cap mine this week, so I will post when I do.

BTW- thanks for the advise on the traces. They look really cheap, almost like aluminum foil as apposed to tinned copper.

-Jay

[smccusker]

replacing the electros didn't make any difference and then unfortunately i completely botched desoldering the 4049 and now i think i've killed it. I think it might be time to cut my losses and just rebuild the circuit from scratch. The hot tubes doesn't use a 78xx regulator chip, it has a zener and a transistor and some other stuff, and it runs at only 9v anyway. I can't decide whether i should make use of the transformer and whip up a 7089 regulator supply with a fullwave rectifier or if i should just stick a dc jack in.

[anticpunk]

I personally am of the mind that keeping high and low voltage as far apart as possible is a good thing. That being said, with proper sheilding an on board xfmr probably isn't too awful really.

Why not just desolder the 4049 and then socket it and replace the chip with a new one. They are pretty cheap after all. I had to do that in a repair to one of those Snarling Dogs Mold Spore units when the Lm324 crapped out. Much safer for the poor chip also.

Just my $.02

-Jay

[smccusker]

thats exactly what i did, and as i was desoldering the traces started to lift. i tried to save it but i think it's gone to heaven.
hah, sorry to hijack your thread with my hot tubes issues, but thanks for your help all the same.

[anticpunk]

Hey, no worries about the thread. I get the feeling that alot of people don't give a crap about the old EH stuff unless it is flawless in funtion.

Why not just bridge the traces with pieces of component leads? I always save what I trim off of the resistors/caps/transistors for use as Jumpers. replace the trace.

I just hate to see a Vintage EH unit get scrapped.

Best of luck with it though if you do decide to scratch rebuild it. I have heard that they are similar to the Craig Anderton Tube-Sound fuzz in circuitry, which seems pretty straightforward. Plus it will have a cool EH case to live in. I assume the case has the graphics in red and black?

-Jay

[smccusker]

I might try to salvage it, i suppose, but i figure if i go to the trouble of patching it up, the original problem might not have been solved which would be annoying. a scratch rebuild might be a bit drastic, and i would be sad if the new one didn't have that "vintage mojo", but it seems to be a solution to both problems i'm currently having with it. i will always keep the original board on hand just incase i have a brain wave one day and decide to nut it out, in which case i will have two, and two is better than one 

here is a picture of the case i found on the net (from http://www.geocities.jp/dotculation/hottubes.html). its not my actual pedal, but its in pretty similar cosmetic condition.

[sfx]

I used to have a vintage Clone Theory and it was also extremely noisy. I loved the chorus/vibrato effect but the noise was just too high for me and I eventually sold it.

I think its just the nature of the beast for these guys. I wonder if a wall-wart power supply (read: get the PS out of the enclosure) would quiet things down.

[anticpunk]

smccusker: Vintage mojo is exactly what I like about all the old EH stuff. That case is exactly the type I remembered. good pics of the guts on that page also.

SFX: I took the PS out of the box and replaced it with a charge pump to make the required voltage from a wallwart. The noise is no better unfortunately. Hoping a recap would help. Bought a 2nd Clone Theory, based on modern style modulation (3007), and it works like a champ with no mods. I think the noise must be characteristic of the SAD1024 based units for whatever reason.

-Jay