KAT 6550 C11 PIO did sweat !!!

[LSfarzo]

Thank you all !!

You've really very kind to me.
I ordered some cheap stuff, will replace the old components and check voltages.
Maybe I'll post the results and if everything is fine will begin considering what to replace with better components... My KAT sounded really good!

Will let you know!
Luca

[LSfarzo]

Dear all,

first of all thank you all for your kind help, especially to John for the caps!.

I made a first basic replacement only of R35 and C11 (which did leak and is electrically opened).
I know.. I have not been very clever since I was supposed to swap coupling caps,cathode resistors and cathode bypass caps but now I have not so much time due to heavy workloads and so I started making a basic replacement to see how think go.

First of all: it sounds good again!

Now the voltage checks are:
1 ) V4 p1 is 88,6 V and V3 p1 is 95 V while they should be 125 V
2) V4 p2 and V3 p2 is 0 V as thery are supposed to be
3) V4 p3 is 77 V and V3 p3 is 88,8 V while they should be 95 V
4) V4 p6 is 151 V and V3 p6 is 101V while they should be 130 V
5) V4 p7 is 1,44V and V3 p7 is 1,72V while they should be 1,6V
6) V4 p8 is 6,9V and V3 p8 is 6,7V while they should be 6,5V
7) V6 p8 is 43V, V8 p8 is 42,8, V5 p8 is 43,8 and V7 p8 is 41,8 while they should be 42V
8) V6 p4 is 427V, V8 p4 is 424V, V5 p4 is 420, V7 p4 is 424 V while they should be 435V
9) ECF80 heater voltage: V1 p4-5 is 5,82V and V2 p4-5 is 5,82V while they should be 6,3V
10) 6550C heater voltage:V5 p2-7 is 5,99, V6 p2-7 is 6,00, V7 p2-7 is 5,94, V8 p2-7 is 5,99 while they should be 6,3V
11) choke 1 p2 is 435V while it should be 450V
12) choke 2 p2 is 441V while it should be 465V
13) positive terminal of C5 is 341V is 435V while it should be 360V

If I am not wrong points 2 and 4 are out of a 10% range around nominal values do you think these values are still acceptable?
Should the values be not acceptable, could this fault be caused by ECF 80?
Just a bit of info: I am using a couple of NOS Telefunken E80CF.

Last note: C11 is the cap which leaked and I swapped it with an orange drop of the same figure. I have found that C12 has a very little oil leakage , too though it measures good figures, so, for now,I did not replaced it for now.
The other two coupling caps (C13,C14) seems to be fine outside (no leakage) and electrically.
Now the point is: don't you think there should be something happening which causes C11/C12 suffering?

Anyway, again, let me say thank you very much you all for the support.

Kind regards,
Luca Sfarzo

[Richard]

I really can't believe I'm reading this

[LSfarzo]

Sorry Richard,
I do not understand.

If I offended somebody' feelings or I was not polite I beg for excuses, I did not mean doing so.

Otherwise, please, could you let me know what I did wrong?


Regards,
Luca

[Desmodromic]

Originally Posted by LSfarzo

Dear all,


Now the point is: don't you think there should be something happening which causes C11/C12 suffering?

Anyway, again, let me say thank you very much you all for the support.

Hi Luca, they guys did answer this question at the start of the thread. The PIO caps suffer due to age. You should really replace all 4 and be done with it.

Good luck.

[bob orbell]

Originally Posted by Richard

I really can't believe I'm reading this

And I thought that I was the only one who gets wound up with others not listening , oh well, I suppose we all have bad days, don't loose heart Richard.

[LSfarzo]

Ok,
I got the point (thanks Desmodromic): I made a silly and inappropriate question since I have already been given the answer

Richard, Greg, John, I apologize.

Since I do not want to cause other damages to valves or OPTX so I will follow your suggestin and replace the cath resistors, the other coupling caps and cath bypass caps.

Regards
Luca

[Greg.]

Hi Luca,

No need to apologise. We all make mistakes, over look things or fail to pick up on advise given. I am equally guilty of that. It is easy to do. I am happy that you will shortly have your amp restored to full excellent performance and reliability. After all, the important thing is that you continue to enjoy the music you love to listen to.

Greg

[Richard]

No offence taken or intended Luca. The power supply to the ECF80s at Point B is common to both channels. When the output stages are repaired and stable check for approx 370V at Point B on both channels. Then record all the voltages for V3 and V4. Then swap them over and record them again. If the voltages move channels with the valves the valves are the cause but they may still be working fine. If they stay with the amp positions then check the resistor values carefully to see why.

[Yellow]

Hi All,

Well, it seems to have been nearly two and half years since I was on this forum, and I think I know why!!! (I now have a little boy who'll be two at the weekend!!). Great to see the Forum is still running with great advice from many of the guys who served the WAD Forum back in the day!

I found this thread of particular interest as I have some AN PiO caps in my pre-amp which I think have been there since about 2001. So, if my maths serves me correctly, that's 14 years!!! Crumbs....where did that time go?? I'm going to take a peak inside when I can to see if mine are leaking. In an odd kind of way, I hope they are, then it's a damn good excuse to explain to the Mrs that I need to upgrade!!!

All the best,

Neil.