A new 12 000 - still working - update

ReidarNikolai · Post by **ReidarNikolai** » Wed Sep 16, 2015 3:14 am

I did read wrong - will fix after forming is done

R

Carbia · Post by **Carbia** » Wed Sep 16, 2015 3:16 am

Ok, so you have to solder one of the wires to the 120v tap and the other one to the common.

ReidarNikolai · Post by **ReidarNikolai** » Wed Sep 16, 2015 7:15 am

OK. Fired it up

I am good on the primaries and got the bias up.

When I flip the stand-by the mains fuse go:
I have followed NightOwls instructions except for the part about the stand-by switch.
My PT is a Marstran T2562 with a lower voltage. So I have soldered the secondaries to the upper part of the standby switch
The diodes to the middle of the same switch. The bias from the PT directly to the 27k on the mainboard. I got 100V there..

I have attached som pics:

Suggestions?

Thanks
ReidarNikolai

Carbia · Post by **Carbia** » Wed Sep 16, 2015 1:04 pm

Those diodes are touching??

You may have a short there.

Ah, I use a light bulb in series with the wall current for these tests.

If you have a short, the light bulb will light a lot and the fuse will not blow.

if the amp is fine, the bulb will only turn red

ReidarNikolai · Post by **ReidarNikolai** » Wed Sep 16, 2015 4:14 pm

Thanks for the suggestion:
Sadly no - the diodes are not touching each other. If you mean where they cross..

What about how I wired the standby switch?
I think it is right..

Another thing is that this did not happen while i was forming the caps.
After that I have just added the 0V from the PT to the Eries -
and fixed the indicator by soldering it to the main fuse (with the COM from the PT) and the 120V tap from the PT.

Suggestions anyone?

Thanks
ReidarNikolai

Carbia · Post by **Carbia** » Wed Sep 16, 2015 5:51 pm

0v from the PT?
do you mean the Center Tap?

Unsolder the indicator and see if you keep blowing fuses.

It's weird to blow the mains when you release the stand-by.
Normal thing is to blow the HT fuse.

ReidarNikolai · Post by **ReidarNikolai** » Wed Sep 16, 2015 10:30 pm

Yes, center tap. On the Marstran drawing it is referred to as 0v, sorry.
Did not help.

I also installed preamptubes, but I can't see them being the reason.

Thanks
ReidarNikolai

Carbia · Post by **Carbia** » Thu Sep 17, 2015 3:16 am

If without tubes you don't blow and with preamp tubes you do, you know where's the problem.

To reduce posibilities try onli v1, if doesn't blow, unplug it and plug a tuve en v2... keep trying until you find the tube that makes your fuse blows.

ReidarNikolai · Post by **ReidarNikolai** » Thu Sep 17, 2015 12:42 pm

So I took out the preamptubes - the fuse is still blowing

The only thing different from when I formed the caps now is the center tap connection - and the 2 resistors that I used while forming..
Attached is the drawing from the Marstran site on the PT:

So:
the Common (orange) goes to the Mains fuse.
the black and green goes to the standby-switch
Yellow goes to power board - diodes and Eries
Green goes to bias tap on the mainboard
White to ground

Is this right?

Thanks
ReidarNikolai

Carbia · Post by **Carbia** » Thu Sep 17, 2015 1:04 pm

The yellow goes in between the two main filter caps.

You can see that those two caps are soldered in series, I mean, you can see that the negative of one of those 100uF caps is soldered to the positive of the other one, right?

The yellow wire has to go there.

ReidarNikolai · Post by **ReidarNikolai** » Thu Sep 17, 2015 3:03 pm

That was it.
And also why I routed the cable up there in the first place..
Which I forgot yesterday..

I´ll get back if I get sound

Sorry
ReidarNikolai

ReidarNikolai · Post by **ReidarNikolai** » Fri Sep 18, 2015 4:00 am

I have no voltages to speak of on V1 and V2 - I have fairly low voltages on V3 (around 80V on pin 1 - should be about 230)
When I probe on V3 I get sound from probing. No sound when I probe on V1 and V2..

Not sure where to start troubleshooting.
Could this be a bad cap or something?

None of the tubes are seriously red or anything.
The power tubes are biased at around 30mV and I have about 500V on pin 4.

BTW - no voltage also without pretubes so I don´t think this is a tube problem..

Thanks again for suggestions

Reidar

Carbia · Post by **Carbia** » Fri Sep 18, 2015 5:19 am

Could be anything

unplug the tubes and check the voltage on each filter capacitor positive pole.

You should have high voltage on every positive pole, with the exception of the ones that are in series, in which the the positive of the cap that is attached to ground is half the voltage.

If there's no high voltage (in the range of 400-500v), you probably have a problem on the supply board.

if the voltages are strong without the tubes, you'll probably have something wrong with the mainboard or the tubes wiring.

tell us the resoults

ReidarNikolai · Post by **ReidarNikolai** » Fri Sep 18, 2015 5:34 am

Thanks C - good of you to help me:
Also thanks for the explanations

Mainboard
Erie: nothing

Power Board:
Rifa: 527Vdc and 278Vdc
Eries: 530Vdc and 265Vdc

TAD - on chassis: 95Vdc??

Thanks again
Reidar

ReidarNikolai · Post by **ReidarNikolai** » Fri Sep 18, 2015 6:49 am

OK.
I took out both AB resistors. The 10k measured 17k so I put in a new one (measuring 10k).
When I powered up again I had attached a DMM clip to the F1 cap (TAD) - when I flipped stand by it went straight 150Vdc - and then it slowly went dont to about 70Vdc.

So what do do?

ReidarNikolai

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