Metropoulos Forum

Just getting parts together for my upcoming 12XXX buildup. If I'm doing anything wrong, feel free to tell me I'm an idiot, lol. I've been collecting vintage and correct parts for my build (I do have a few tan resistors that are new for mockup purposes only). The resistors are Piher and Beyschlag mostly. I like vintage original components and will most likely change out the tan and grey resistors for vintage original brands if I can find them. The wattages here are intermixed 1/2 watt and 1 watt (68ks are .33 watts and 470ks are .8 watts) The 820R, 470R and 82K are larger wattages than usual as it's all I have. Still missing the flat ceramics.

Seems to be fine.
Super lead. Nice choice.
Adding one wire from the power board to the main board...
One resistor at the bias pot...
And these caps, the flat ones... (bright ch. mix and tone stack treble)
Can not tell much about the values though, but you seem to be accurate in what you are doing so my guess is that everything is OK.

Nice components!!! Will become one great amp.
Envy

Thanks for the pos input. My values are all good to go. I'm trying to go as period correct as I can. I just snagged some 560pF, 556pF and 250pF flat tone/bright caps and a correct bias resistor today. Also found some more Piher and Beyschalg resistors I will swap into the mix on the bias side of the board. So hard to find the yellow Iskras. My wattages are not all spot on (68K 1/3watt, 470K .8watt, 10K 1watt) but I just scored some 68K 1 watt and some 27K 1/2watt, both Beyschlag. Would love to find some good usable/original Dalys but that's asking a touch much. I even have some original used trannys that I sent to MM to have rewound to spec. Just got the rest of the parts and will start the build again after Xmas. More pics to come.

Cheers!

I added a few more pics of where I am with my amp. I will try to post a step by step section after completion. Cutting wires to length, testing continuity from turret to pots, jacks, etc. So far so good.

How is your build coming? I'm almost done with mine(12XXX). Still lots of questions.

I have been out of pocket for a while now and still haven't finished my build. Was goig to sell it but I figured I'd go ahead and just get it done. Will have it completed first of the year.

So.........

Still pluggin away

another pic

Great to see an update! You should keep the wires (from the bridge rectifier to the first positive terminal of the mains caps and the center tap from the PT) in an accessible spot so you can reform those caps before cranking up the amp for the first time. With that blue 32-32 Erie cap on the board, does anybody know how that one can be reformed while it is in the amp. Stunt Double sent me one, but I'm wondering if it can be reformed while it is on the circuit board. Can it be done along with the mains and screens? Can this cap be set in hot water to speed up the forming process?

Strat78 wrote:Great to see an update! You should keep the wires (from the bridge rectifier to the first positive terminal of the mains caps and the center tap from the PT) in an accessible spot so you can reform those caps before cranking up the amp for the first time. With that blue 32-32 Erie cap on the board, does anybody know how that one can be reformed while it is in the amp. Stunt Double sent me one, but I'm wondering if it can be reformed while it is on the circuit board. Can it be done along with the mains and screens? Can this cap be set in hot water to speed up the forming process?

The output of the bridge rectifier (red wires) will connect to the positive terminal on the nearby mains cap, AND to a wire running to the fuse. If the forming resistor is the only thing connected to the bridge, and these two wire are connected to the other end of the resistor; all downstream capacitors(Screens, PI and preamp) will also be formed. Of course you have to be sure the fuse is in!

Problem is, in this pic both connections are made to the bridge... it would be easier if the fuse wire was connected to main cap. Then you could just insert the 100k resistor between the bridge and the lone red wire for forming.

I just followed Georges diagram with this board. Are you saying that if I de-soldered the connection of the 2 red wires (bridge) and soldered the resistor to that turret instead and placed both de-soldered ends of the 2 red wires on the other side of the resistor it would work for all the caps at the same time? Like the pic below?

That looks like it should work. Might be better to just move the fuse connection to the + side of the Mains cap.
Keep in mind that I have not done this with a 12xxx yet... but it looks right to me.

Don't forget, the tubes must be out, and the PT center tap should be disconnected from junction of the mains cap. Looks like it would be easiest to lift(and tape off) the yellow wire in your pic from the PT.

Here is the thread on forming:
http://forum.metroamp.com/viewtopic.php?f=4&t=8396

Thanks. I could do the fuse wire to the + main cap and run the resistor from + main to bridge. Same thing I guess.

Well, finally after putting my project off again and again, I finally got it up and running. Sounds better than I expected. Still in the tweaking stages but I'm very happy with it. Lots of gain and the tone is right where I wanted it to be. Meaty but tight bottom end, loads of midrange and not to thin and tinny on top. Here are a couple shots. EL34s are Winged C ( SED) and the preamps are Mullard re-issues for now. After the tweaking I have a Tung Sol for V1 that I am going to try. Now I have to figure out how to post some sound clips... Enjoy!