PT weirdness

[Madison]

It's like diodes aren't doing their job.
Hooked up both styles of full wave.Even tried half wave.
ie the 320-0-320 taps and after diode rectification I get 310 VDC.

Also
When I ground the PT CT ie on the 320-0-320 the two 320 taps read 680VAC.

The PT specs are 350V-320V-290V-0-70V-290V-320V-350V Dc150mA / 6.3V-2.5V 3A / 6.3V-2.5V 3A / 6.3V-5V 3A
with a copper shield.

I hooked up a 5Y3 tube and it worked properly.

[stratele52]

It's like diodes aren't doing their job.
 
I hooked up a 5Y3 tube and it worked properly.

it look it is the silicon diodes are bad .

Easy to check with Ohmeter.
 
1 K ohms scale . Positive probe on anode , negative probe on cathode ( white line)   ; very LOW reading
                        Reverse probes ; HIGH reading or mostly infinite.
                       

[Madison]

I'll check.

Would a diode failure hurt the PT?

Thank you.

[sluckey]

ie the 320-0-320 taps and after diode rectification I get 310 VDC.

Did you have a filter cap connected? DC voltage reading will be low if not.

When I ground the PT CT ie on the 320-0-320 the two 320 taps read 680VAC.

Are you saying that measuring voltage BETWEEN the 320 taps is 680? Or do you mean you are measuring 680 from CT to each 320 tap?

The only reasons for the tube rectifier to work but diodes don't work would be faulty diodes or you wired the diodes wrong (in which case one or more diodes are bad now). Shorted diodes will harm the PT. Open diodes will not.

[stratele52]

I'll check.

Would a diode failure hurt the PT?

Thank you.

It could , but your voltage reading look good

[Madison]

ie the 320-0-320 taps and after diode rectification I get 310 VDC.

Did you have a filter cap connected? DC voltage reading will be low if not.

>>>No change

When I ground the PT CT ie on the 320-0-320 the two 320 taps read 680VAC.

Are you saying that measuring voltage BETWEEN the 320 taps is 680?

>>>Yes.


The only reasons for the tube rectifier to work but diodes don't work would be faulty diodes or you wired the diodes wrong (in which case one or more diodes are bad now). Shorted diodes will harm the PT. Open diodes will not.

Here is what happened.
I had the amp running and then I rewired it to have a CF.(I checked the wiring multiple times)
I turned it on, it fried the 4.7K/5W power rail resistor.
I kind of figured the diodes went bad.
The readings are 680V with no load.
I decided to put a cap on there just to see and it got hot.
I wired it like the attached pic but with only two 4007 diodes.

Wired this way, open diodes, the PT would be okay?

So anyways.
I bought another PT and I am getting the same readings.

Now, I believe MM is FUBARed.
Can't get a reading off a 1M pot over 2k.
Ordering a new one right now.

I have some real shitty luck with this stuff.

[stratele52]

If you fried a resitor ( or any parts ) , problem is AFTER  the resistor , never before ( diode ) .You have a problem AFTER this 5 watts resistor . Check that and fix it before .

Use a current limiter when power ON amp first time . You know , 100 watts bulb lamp in serie between wall outlet and your amp power cord.

Open diode won't damage Power Transformer.

"......to have a CF "  What mean CF  ?

"......I believe MM is FUBARed."     What do you mean ?

[Madison]

"......to have a CF "  What mean CF  ?

Cathode follower

"......I believe MM is FUBARed."     What do you mean ?

Multimeter is .........well you can look up "FUBAR" on your own.

Thanks.

[stratele52]

"......to have a CF "  What mean CF  ?

Cathode follower

"......I believe MM is FUBARed."     What do you mean ?

Multimeter is .........well you can look up "FUBAR" on your own.

Thanks.

Thank's Madison

[Madison]

Doubled up on the duh duh duh diodes.
Looking good for the moment, with no load.
Hopefully the PT will survive under pressure.

[stratele52]

Doubled up on the duh duh duh diodes.
Looking good for the moment, with no load.
Hopefully the PT will survive under pressure.

And what about that ? ;Use a current limiter when power ON amp first time . You know , 100 watts bulb lamp in serie between wall outlet and your amp power cord.