Paramour 1 Troubleshooting

[Doc B.]

You have test the diodes and they are OK, so it's probably the filter caps.

[Paul Joppa]

First thinh is to check the DC resistance of the power transformer windings. Sorry I don't have the right numbers here - maybe someone else does?

[jeff g]

are these the correct PT readings (from a post of yours awhile ago)?
assuming I've got the Hammond PT - I'll check when I get home.

 
http://www.bottlehead.com/smf/index.php/topic,1308.0.html

Do the resistance checks in the manual first. Note T25 should be 200 ohms, not 2 ohms, if that typo has not bee marked in your manual yet. While doing that, look for electrolytic caps that are bulging at the ends. Also, while you are in there with the ohmeter, check the resistance of the power transformer high-voltage windings. You should have the Hammond power transformer (label on the back side of the core). The black and white wires are the primary and should read about 10 ohms. The high voltage secondary are the orange, brown, and violet wires. You should read about 200 ohms brown to orange, 220 ohms violet to orange, and 420 ohms brown to violet.

[jeff g]

You have test the diodes and they are OK, so it's probably the filter caps.

I have some 47uf 450 v axial caps on hand but they're smaller than the radials currently installed.  would they be suitable (at least for an initial test)?

Panasonics I think - maybe not high enough temp rating?

[Grainger49]

Yes, that is a reasonable conclusion.  IIRC, you swapped the tubes so it isn't a shorted heater.  That only leaves the transformer and input wiring.

Just to be sure first clip the two diodes, bend them so they are obviously open.  That leaves the transformer with no load, no diodes and caps.  Try powering it up one more time and check the fuse.  If it blows, it is the input wiring shorted somewhere after the fuse or a shorted transformer.

Maybe Doc or PJ can give you resistance readings for the primary and secondary sides of the transformer. 

If the fuse holds then two caps, two diodes and a resistor will put you back listening to music.

[jeff g]

Yes, that is a reasonable conclusion.  IIRC, you swapped the tubes so it isn't a shorted heater.  That only leaves the transformer and input wiring.

Just to be sure first clip the two diodes, bend them so they are obviously open.  Do you mean remove them ?

That leaves the transformer with no load, no diodes and caps.  Try powering it up one more time and check the fuse.  If it blows, it is the input wiring shorted somewhere after the fuse or a shorted transformer.  It might be the trasformer - there was some 'minor' arcing during one of the tests.

Maybe Doc or PJ can give you resistance readings for the primary and secondary sides of the transformer. 

If the fuse holds then two caps, two diodes and a resistor will put you back listening to music.

[jeff g]

I'm pretty sure I've got the Hammond transformer - are the values I quoted before the correct ones?

Grainger - I'm not sure if it was clear in my quote, but did you mean to remove the diodes then test again?

[Grainger49]

Yes, the diodes probably cost 17 cents so replacing them is cheaper than replacing the caps.  I just wanted to prove that your transformer and associated wiring is OK. 

Clipping the diodes is faster than desoldering them.  You have narrowed it to the power supply.  This is another check to see if it is the transformer/wiring or diodes/caps/resistor.

[jeff g]

I removed the diodes - measured resistance at infinity

Tried firing up again - fuse blown.

Removed all PT wires- they test as follows:

Black-White 10.8 ohms
Brown-Orange 83 ohms
Violet - Orange 175 ohms
Brown - Violet 93 ohms
Green-Green 1.5 ohms
Yellow-Yellow 0.6 ohms

Black - Transformer housing infinity

all the secondaries seem low relative to the PJ post I quoted above.

[Grainger49]

Jeff,

I'm hoping it isn't the transformer.  Is it possible any one of those few wires from the incoming cable to the transformer has come loose and grounded?

My Paramours are the newest transformer (lugs under the chassis) so I'm thinking my measurements wouldn't help.

[Paul Joppa]

It sounds like a bad transformer to me. I wish it weren't too! I'm out of town, and I think Doc B is also at the moment. I'll email him. Meanwhile, make the same check on the other channel's transformer - that should eliminate other possibilities.

[jeff g]

the wires from the incoming cable seem ok.

I guess I can check the other channel - hopefully I won't monkey up a working amp!

if it is the transformer, could someone please recommend replacement options (keeping in mind that while the MQ stuff would be nice, it's not really in my budget right now)

[jeff g]

I checked the PT on the good channel - readings were different (and close the ones posted by PJ above)

Black - White 10 ohms (10ohms on bad ch)
 
Violet - Brown 411 ohms (89 on bad); should be 420
Violet - Orange 212 ohms (168 on bad); should be 220
Brown - Orange 199 ohms (79 on bad); should  be 200

So, is the PT shot?  Wouldn't some of the measurements be very low or open?
 

[Doc B.]

Yes, it sounds like a partially shorted secondary winding. It will need to be replaced, and it will probably be wise to replace the rectifiers as well.

[jeff g]

thanks Doc.  I've got an order in for caps, rectifiers...

Do you have any suitable transformers for sale?  or recommendations ?