• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Melos GK-1 Tube Pre-amp Schematic needed ...

Thanks John. If I come across a Melos archive, I will get back to you. Melos went out of business. Then, some years ago, I remember seeing the Melos technical archives up for bids on the internet. I remember thinking that it would be a good idea to broker this collection. I was down in cash, but in retrospect I should have jumped. I just assumed that the money involved would be out of my league. I started asking myself questions as to how I would recoup my investment, and more. I wonder what happened to all that stuff!!!??? SOMEBODY must have it and is sitting on it.

I am on the last finishing touches to restoring my GK-1 power supply. But once again, I am being held up by priorities at work. I should be finished in a couple of weeks, and if it doesn't smoke, I'll put a note on this thread for any dull amateur like me who wants to follow. I made some changes due to parts restrictions, and I seriously upgraded a heat sink. I think that the stock PS module ran too hot. I may have to add a fan, or replace the slotted hood for screen or mesh. ÑÊCheers, Lorne
 
Hello Lome, ref: my Melos TM90 ST II and your GK. Good luck with your project and I hope you will get the results you are looking forand it is true that some of these units can use a bit of upgrade . The original builders may sometimes skimp on the quality of the parts. Heat displacement is very important in these amplifiers if you want good results. So far, I have tried many places to find the schematics for The Melos TM 90 ST ll,without luck. I emailed melosaudio and they replied by saying that they have no schematics or info on the melos amps, however, they will repair the unit if I sent it to them. It's hard to understand how they can repair it without diagrams or info. These amps a very complicated. I will try to sketch my own diagram by tracing the parts on the board. However, there are 4 IC's missing from the amplifier and I ahve no way of knowing what they are, so that will present a problem for me. I hope if anyone has any info on this amp, that I will hear from them soon..

John
 
It's hard to understand how they can repair it without diagrams or info. These amps a very complicated.

The Melos archives appear to have vanished, and I believe that the company you mention is not in possession of documents that are of a type that can be distributed or shared with anyone. I have to troll deep in my feeble memory, but I seem to recall that the company was founded by a person/persons who were ex-Melos employees. They depend on memory and intimate knowledge. Of course, one can imply from this that they can produce their own INTERNAL documents for use among their own employees for use at the bench.

I got loaded down with work, so the final touches to my rebuilt power supply board are waiting until I finish the backlogged priorities. It sure looks different than the stock board by now. I SHOULD take it to a tech and have it powered up on a variac, but I may get impulsive and take it out on the driveway on a long AC cable and ...?

Your needs are more extreme than mine as I had a working unit. All the parts were in place. When I faced a dilemma in regards to some unusual caps, I bumped into our city's foremost tube guru Ñ a pro who rebuilds all manor of classic tube gear as well as constructs. He could analyse the board at a glance and gave me some alternatives to consider. I was thus able to source available caps for the purpose (yeah!).

Good luck! In the meantime, I'll keep my eyes out for both of us and I trust vice versa.
Lorne
 
REF: Melos GK-1 and TM90 st ii. Thanks Lorne for your prompt reply to my post. From you info I think I got the picture. seems like they may have skuttled the company and everyone went away displeased with each other. In this case all trace of any documents have vanished. I will keep my eyes opened for any information that pops up. Again good luck on your project and dont be afraid to fireup that unit. Reminds me of the first time I built a transmitter and was afraid to power it up. All I had to do was plug it in and throw the switch. So, I called my girl friend and had her turn it on for me.. well, it did not smoke. It worked fine..Be Well

John