Vintage amp restoration and Beyond

[karpathion]

Nope, sorry... too stoned or something; I meant the Windsor

It's 4:40 AM here, I should go to bed.

Go to bed!  :old:

[GoldenVulture]

I'm going to have to order some more pots and a fuse holder. The one in it broke on me, a bit old and brittle. Ive got to organize a better power cord connection too. The amp originally had a round socket arrangement but it had fallen a part.
It uses 1 meg pots for vol control. I need a few 250K pots for the tone too.

Tossing up replacing the can caps in it. I might get the pots first and see how it goes and decide from there.
[ 4 x 100uf/350 volt - 1 x [ 22uf x 4 ] 400 volt ]

[karpathion]

I think that particular setup is worth throwing a little coin at. You have all kinds of option, plus transformers that can handle almost anything.

It's almost a Plexi/800 anyways. 

"Much fun you can have with that one. Strong with the dork it is!"

:toast: 

[GoldenVulture]

I don't know if you noticed this on the Eminar page atOzvalveamps.
Really interesting what this guy says.

More memories

By: genpk on AGGH, August 30, 2005, 08:24:12 AM

Hi guys, saw the post on Eminars which I have done quite a lot of work on over the years.

History as I know - Made in Melbourne from about early 1970s to about the last one I saw was dated 1982 I think and was numbered 2750 ish. As mentioned transformers were built like trucks and made by a company called TRIMAX. TRIMAX was bought out by Ericson Communications and eventually mothballed as it was a competitor to them. I have seen late model Eminars with Ericson badged transformers.

They were built as a cheap alternative to both Fender and Marshall imports which at the time were expensive due to Aussie import duties. They built a 40 watt, a 100watt and a 150 bass head as well as 100watt P.A heads.

They had a unique setup for their time on the output tubes using grid resisors to enable the output to use either EL34s or 6L6 tubes with readjusting bias control.

Many of the capacitors were the same parts used in english JCM 800 and according to my findings circuits were either wired as an JCM 800 type amp or a Fender twin type setup depending on what was required. In an article Ritchie BLACKMORE mentions an Eminar bass head to be a head to find for a great sound.

They can be configured to just about anything as they are basically point to point wiring. They are a very powerfull amp and on the 150 watt models can have up to 700 volts going to the output tubes (not many current tubes can handle that). Maybe a candiate for KT88s.

Can be suseptable when power spikes occur, takes out power diodes or output transformers. All in all, one of the loudest, cleanest amplifiers you will ever hear. The quad boxes had celestion green backs or G12s in them - yes as stock standard!!!!

[GoldenVulture]

I used to have one of these backin the early 70's. It came with a pair of quad boxes. The output was a quad of 6cA7's and it was fucking loud. I managed to melt a valve socket in it while jamming one day.
I can't remember it having the presence control but it sounded better than a lot of other models from the same company. I'd love to find a circuit for it just to know what was actually going on in it but sadly they seem non existent.

[karpathion]

I can't find anything on it either. Mainly just you talking about it on SD. That one may be lost to history.

Are you leaving the preamp alone for now on your project? I'd be curious to hear what it sounds like with the current circuit. Maybe split your guitar signal and hit both sides. It probably won't sound too bad.

[GoldenVulture]

I can't find anything on it either. Mainly just you talking about it on SD. That one may be lost to history.

Are you leaving the preamp alone for now on your project? I'd be curious to hear what it sounds like with the current circuit. Maybe split your guitar signal and hit both sides. It probably won't sound too bad.

That's my intent, finish it as it is and then see what it sounds like. Depending on that , maybe  do a full conversion .

 I Just need to do the pots and clean up a bit of wiring and I'm ready to turn it on. I don't know why I didn't get back to it sooner. Depending on what it sounds like it is a potential candidate to mod like the windsor to a full on 2203 conversion, poweramp and preamp.

I've just ordered some pots and a fuse holder. They'll take a few days at least to get here.
If I did all the big cans in it it's about Aus$70. One can is a multi can the likes of which I can't find yet. 4 x 22uf/400V.
I might have to make a replacement pack for that if I go into changing them.That'd be another $20>$30.

[kinnikuman]

This is cool

[karpathion]

This is cool

If you look at the schematics for a second, the cool factor goes up even more. Stock, that amp is pretty much a Plexi.

[karpathion]

You get anywhere on this one yet, or are you waiting for the other components to come in?

Do you have a signal generator or Variac? You may want to check that OPT primary. You mentioned that they were prone to spikes and burning up.

From the absurd amount of Marshall circuit info I have absorbed lately,  this was a problem for a couple Marshall models, and many clones of several models.  Apparently those type of amps require a 1.7k or 2.2k primary. 4k or 3.3k primaries where used in many cases. Or something like that...

Yours is probably right, but it might explain the OPTs popping on them in the past. The 1.7k is what you are shooting for, I believe. Do you know your exact PT secondary voltages yet?