Cathode bypass upgrade

[srhombeus]

Hi,while i was reading Mr. Joppa's old writings,i noticed something.

" The output tube cathode bypass capacitor (which is on the PSU board) can by bypassed with a film cap across the cathode resistor, T6-T16 and T10-T20. To completely replace the electrolytic, simply remove the wires from T1 and T5 to the PSU board "K" connections.The best place for film bypass capacitors in the power supply would be from the B+ outputs on the PC board, to the nearby cathode resistors at T1 and T5. An extra hole is provided on the PC board for this. "

I read that there are some mistakes in this process.I would like to do this update,but i would like the learn the right procedure. To summarise,the thing that i should do is :
1-Remove the wires from Ks to 16U and 20U.
2-Solder min. 47mf film caps between 16U and Hv+ and 20U and Hv+.

Is this procedure correct? I'll be happy if i get some reply from you.
Thanks.

 

[Paul Joppa]

That describes two different operations on two different capacitors, and your description mixes them up. Don't do it that way!

I am unaware of a problem with my suggestion - can you find a reference for it? I won't clarify my notes until I know what problems there may be - no sense re-iterating bad advice!

 

[srhombeus]

Sorry for my misunderstanding,i realised that last night while i was thinking.i read there are some mistake in the terminals in this link :
http://bottlehead.com/smf/index.php?topic=3300.0

i dont understand the terminals T1 and T5 for example,isnt that only one channel ?
the process would be solder the leads of the films caps to 16U and 6U - 10U and 20U ?

Ä° have one pair of mcap 47mf in my hand,after soldering them to these terminals,do i have to remove the wires to Ks or let them ?  Ä°'ll be really happy if you can explain this process step by step because i dont want to do some mistake in the circuit.

Sorry again for my misunderstanding..

 

[Paul Joppa]

Later in the thread you linked, I noted that the mention of terminals T1, T11, T5, and T15 was an error.

As in your original quote from me, and as you just described, one cap goes from T6 to T16, the other from T10 to T20. With this arrangement, the cap is in parallel with the stock 220uF on the PSU board, so it serves as a bypass.

You can optionally remove the wire to the K terminals on the board; this will disconnect the 220uF cap leaving only the new 47uF caps. You may or may not hear a difference if you do this.

 

[srhombeus]

Later in the thread you linked, I noted that the mention of terminals T1, T11, T5, and T15 was an error.

As in your original quote from me, and as you just described, one cap goes from T6 to T16, the other from T10 to T20. With this arrangement, the cap is in parallel with the stock 220uF on the PSU board, so it serves as a bypass.

You can optionally remove the wire to the K terminals on the board; this will disconnect the 220uF cap leaving only the new 47uF caps. You may or may not hear a difference if you do this.

Thanks for your clean explanation Mr. Joppa,i will solder the new caps to the terminals and remove the wires on Ks. Ä° understand that there wont be any dangerto do this,and i hope there will be some improvement in sound quality.

 

[Paul Joppa]

There are always dangers when you change a developed design. I make no promises - modifying our kits is always a risk the owner must take.

I don't see any risks except for the cathode resistors which do get pretty warm - keep the 47uF from touching them. But I can't guarantee there are no risks that I failed to see.

 

[srhombeus]

There are always dangers when you change a developed design. I make no promises - modifying our kits is always a risk the owner must take.

I don't see any risks except for the cathode resistors which do get pretty warm - keep the 47uF from touching them. But I can't guarantee there are no risks that I failed to see.

No explosion,no snoke.Amp is running for 1 hour without any problem. For the improvement,i think that i noticed more silent background and also more developped bass performance..  Thank you very much Mr. Joppa for your help. Next step,i will change mundorf supremes with rike audio in the parafeed caps..