Very interesting, specially that weird tiny reverb tank.

Maybe you can take a gut or sideways picture to show how springs are driven?

It might very well be Piezo at one or both ends, like Silvertone.

As of the rest of the circuit, many of those amps were made for different resellers, often department stores, but by the same OEM supplier, so you might find a very similar one under other brand, with minimal changes.

But as is it looks very well preserved.

Those hand drawn PCBs using flexible black paper tape and stick-on donut pads certainly bring back memories

Back in the day, before widespread personal computers, I used to draw PCBs using Bishop Graphics tapes and pads.

I recently acquired a 1979 Harmony Solid State Piggyback amp with 2x10 (Oxford 10j) cabinet.  Speakers, pots, etc., match the 1979 date.

It looks like online photos of an L-3500 but as you can see from pictures it only has the rear sticker model number 7096-90PB and it was built "after Harmony stopped making amps" sometime in the mid 70s.  No "L-3500 label" to be seen. 

I took photos of the inside and made a little composite photo to make it easier for me to view / trace.

Anybody recognize its guts?  The reverb "works" after I made it float again, but it's pretty weak. 

The tremolo works well, and as a bonus I figured out that you can turn the trem off if you keep turning depth CCW until it clicks (haha). 

Funnily enough (to me at least), they chose Bass to double as the power switch instead of Volume.

I read some stuff the other day about a company called Sound Design Products and a few little Chicago-based outfits that possibly assembled these amps and perhaps had extra stock to build / sell after Harmony closed up shop, but I'm starting to wonder if ChatGPT hadn't just gotten drunk on electrons and started hallucinating a lot of that "information".


Thanks!  (btw, it sounds really cool with the Revv G3 clone pedal from Mosky in front of the amp.)

Also I checked the coil like Mr Jaun said and it seems to match a data sheet I found



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What's weird about the data sheet is I downloaded two pages and I can access and read them etc plain as day but if I try to upload them here they get dim and won't let me do it 

Yes sir thanks definitely better doing it that way if I connect it at voltage I get a click

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If I adjust the power supply "com" and "NC" open at about 16v DC then I have to roll it back to about 6v DC before it closes back up

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Also if I hold the relay while doing that if I don't hear it I can feel it

It might be more obvious without adjusting supply while testing.  Just set for 24VDC and turn on. 
Some are not very loud, put your finger on it and you might feel the click.

Well I tested one of these new relays with a power supply and some leads and a multimeter monitoring continuity.

They seemed to open and close fair enough but I'll be damned if I heard a single click 

Idk maybe it's not supposed to make an audible click

But...I think that's what I am hearing click in the power supply as voltage is increased.

Comparing the markings on the devices I definitely see a difference but idk if that means anything.

Oh well it's not like I spent a fortune 🔮 on these. 

 

1/4 or 1/2 watt in carbon film or metal film will be fine.
Check the dimensions, some of the modern parts are so tiny they can be difficult to work with in applications like this.

Possibly these

I will order those resistors 330 ohm & 4.7k ohm. Schematics don't say, but what type of resistor should I be using "Carbon Film" or "Metal Film". Also what watts should I order those resistors in? The attached picture shows where these resistors have been mounted on another amp and I will do the same to mine.

330 ohm shows mounted on R29,R30
4.7k ohm shows mounted over D5

Hi everyone,

I'm currently working on a personal solid-state amp project, and I'm drawing inspiration from some of the classic transistor amps I've always admired. In particular, I'm looking for the complete schematics of the following models:

Randall RH200 G2 / RH100 , etc

Peavey XXL Transtube

I already have the power amp sections, but what I really need now are the full schematics, especially the preamplifier sections, which are key to capturing the character and tone I'm aiming for in my build.

If anyone has access to these schematics or can point me in the right direction, I'd really appreciate it. I'm also open to sharing schematics or technical info in exchange if that helps.

Thanks a lot in advance!
Raul