1203-80 or not?

[Ralle]

Hey.
I have a Metro Pt... it's ca 2,3" thick... the heater wirers are green/green yellow, and both bias are blue...
The primary terminal has; com, 120, 220, 240 v... the seccondary terminal has; two 178v ( high voltage alternative ), two 152v ( low voltage ) and the center tap
It holds a voltage of 460v at 240v primary... EU ( standby off )
I've seen pics of 1203-80 Pt's that has both 190v ( high ) and 178v ( allso high ) where the low are the same; 152v...
Questions:

1. Is it a 1203-80 that I have ( no stamp or nr on it )?
2. isn't 460v a bit low for the high voltage alternative? The speqs says 490v on high...
3. If my Pt isn't a 1203-80, what Pt do I have?

I bought this baby about 7 - 8 years ago... I know... why haven't I tried until now... well, didn't feel I needed to, until now...

Ralle

[JimiJames]

This one ?

[Ralle]

Yes, only my Pt's primary terminal doesn't have any cables... just the soldering terminals...

[harddriver]

I remember there was a run of dual tap transformers that Heyboer made George that did run a little low on voltage, nothing major. Look at it this way you'll be easier on your Power tubes.

You didn't blow your original Power transformer in your 68 plexi did you Ralle?

Please tell me you didn't, that original PT is part of your amp's magic!

[Ralle]

No I didn't I was thinking it might be getting a bit tirerd and warn out... so I thought I'd have a look at this one...
I wrote that this other pt held 460v... that was unloaded... loaded it has 445 - 450v... Do you know anything about it... is it a 1203-80 or...?

[harddriver]

Sounds like you have a dual tap by the description. It almost has to be if you bought it from Metro(George) and it has the two voltage taps. It is a laydown configuration right for a 68 I assume since you bought it for your 68 amp?

Maybe it is one of those transformers that run a litle low. I would contact George and send him some pics he might be able to confirm it for you.

BTW my 1979 Marshall ran a B+ of 454 volts pretty consistently. It is easier on modern power tubes than 500DCV B+. Let us know what you find out from George.

Do you have any pics of it?

[Ralle]

I'll get right on that... I just have to install a photo program on my computer... I had that a while back, but had to remove it due to hard drive space...
Maybe some of you could post some pics, so I can see and compare... until I have this program up

[harddriver]

PM me your email Ralle, I should have some pics during my build of my 68 metro that has the dual tap that I can send you.

[Ralle]

Pm sent... Thanx man...

[harddriver]

Ralle, the lamination stack on my 1203-80 dual tap is 2 inches from the chassis top(bottom edge of the lamination stack to the top edge of the stack.

Hope this help ya ID it!

[Ralle]

Yes it does... thanx Mark...
You wouldn't happen to have some voltages, would you?


I wrote Brian about it as well... and said the same thing... it looks like a 1203-80...

[harddriver]

It's been so long since I ran it at full 120ACV volts Ralle I can't remember. But mine was on the lower side of the HV spec of 490 for sure. I think mine was closer to 450-460 if I remember correctly like yours reads.\

Variaced down to 88-90ACV mine puts out around 350DCV on the plates on the high voltage taps the last time I had a meter on it if my memory serves me correct.

[Ralle]

This might be a stupid question, but do you think you could check your wall socket voltage? Reason; I run mine at 240 vac ( Sweden ) and I checked my wall socket voltage... it reads lower than it's suppose to; 210-220 vac during daytime, but at night, it gets up to 220vac... I connected the primary th 220 vac one night ( when it was accurat to the wall socket voltage )... and I got 490v... at 240 vac I get 450-460v b+
I just wondered if your wall socket delivered around 110 vac... if it does, it would explain the low b+...
I don't think it's a problem... other than I can't controll the main AC... so I would need a variac to check when ever I play...

[JimiJames]

Conditioner/regulator ? Best to find one used.
It would give you a constant voltage no mater what the wall socket voltage is.

[harddriver]

This might be a stupid question, but do you think you could check your wall socket voltage? Reason; I run mine at 240 vac ( Sweden ) and I checked my wall socket voltage... it reads lower than it's suppose to; 210-220 vac during daytime, but at night, it gets up to 220vac... I connected the primary th 220 vac one night ( when it was accurat to the wall socket voltage )... and I got 490v... at 240 vac I get 450-460v b+
I just wondered if your wall socket delivered around 110 vac... if it does, it would explain the low b+...
I don't think it's a problem... other than I can't controll the main AC... so I would need a variac to check when ever I play...

You're going to have that in your AC supply. Mine flucuates from 110 to 130 depending on time of day and load demands. Yes these ACV line fluctuations account for big movements in your B+, and I have read it is not always a linear interpolation of ACV incoming voltage to what you are seeing on the secondary side of your Power transformer due to inductance and such. Even my furman voltage regulator my ACV still fluctuates some just a smaller range. Yes if you want exact incoming ACV you would have to adjust with the variac every time you fire it up and even then it will still fluctuate.

When I run my 12 series it's what I do, jsut depends on how much BS your willing to put up with?