a few paramount questions

[mdub71]

I am assembling the Paramounts, and having a great time. I do currently have a few questions. I got a bit confused by the instructions on mounting the power transformer. Are there the dark colored fiber washers between the transformer and the chassis plate? Do the lock washers remain between the bell end and the transformer? There are some white/clear plastic washer/spacer things, are those for the 25w resistors? Or, are they for the power transformer? Thanks in advance for the help. matt wills

[fullheadofnothing]

The white nylon washers go in the holes of the power transformer, and isolate the transformer from the top side of the chassis. The black fiber washers isolate the screws from the chassis by having the ridge sit in the hole and prevent the hardwre from touching the bottom side of the chassis. The cylindrical resistors are isolated by a combination of a black fiber washer and a clear (and not shouldered) mica washer. Follow the instructions for the location of lockwashers.

[wullymc]

Good questions mdub,

if one didn't use the white nylon washers(to isolate the transform from the chassis) what would be the fallout?

Any failures?  Potential problems....higher hum? 

After the fact it would be a lot of work to disassemble the power transformer to insert these.

now that i look back it doesn't say to do that in the manual but i see them in the picture.

Thanks...Dave

[Paul Birkeland]

if one didn't use the white nylon washers(to isolate the transform from the chassis) what would be the fallout?

Any failures?  Potential problems....higher hum? 

Noise, failure, destruction of the power transformer. 

After the fact it would be a lot of work to disassemble the power transformer to insert these.

Yes.  I have repaired a Paramount here and there which had the hardware all jumbled up, and it ended up being very time consuming and expensive.

now that i look back it doesn't say to do that in the manual but i see them in the picture.

Second step, page 42.

[mdub71]

thanks for the discussion and the help.
much appreciated.

mw

[wullymc]

Thank Paul for your post.

Definitely going to be taking out the power transformer and installing the washers!

Would there by any visible signs that you could have potentially damaged the power transformer?  Or i guess just retaking the voltages would indicate this.

Thanks..Take care...Dave

[Doc B.]

I doubt it would be damaged. But a transformer in direct contact with the chassis plate will induce eddy currents into the ground plane that can create 120Hz noise in the amp's output. Isolating the transformer laminations from the chassis at the mounting points and running a drain wire from the lam stack to the safety ground lug will remove that issue yet still retain the safety feature of the transformer case being connected to safety ground. It is a very slim possibility, but if there was a short from the high voltage winding to the laminations the connection to safety ground would prevent a shock hazard. 

[wullymc]

Thanks so much Doc!

Nice to know.  i will desolder the power pcb board remove the power transformer and install the washers.

Sorry mdub to steal your thread....and good luck with your build.  As you can see here, wonderful support from Bottlehead!


Dave

[Paul Birkeland]

i will desolder the power pcb board remove the power transformer and install the washers.

If you're really slow and careful, you can undo the bolts on each corner of the power transformer, tape them in place, then let the transformer drop through the chassis a bit, then get the nylon washers where they need to be.

Desoldering that power supply board is a bit of a challenge.

[wullymc]

Great thanks Paul

I will try the tape trick.  i originally took out the top ones (back of the power) and was almost able to get the washers on but then looked at trying to loosen the front screws and it looked very tough.  i will tape over them and give it a shot.

Take care and thanks again for all your help!....Dave

[wullymc]

No go for me.

It is too tight a squeeze for me to try to tape the nuts.  Tried everything.   Ended up getting the 2 washers on the back screws but no luck with the front screws.   In March i will desolder the 12 pins on the pcb and the cables that are on the back of the pcb and flip the pcb forward and remove the power trans.

Take care...Dave