kit 34

[Richard]

Hi Jiten,

Ignore the numbered points in my last post as they relate to a problem which would be common to both channels.

Instead go with the last comment and try replacing the EL34 cathode bypass capacitors C15/16 and C17/18, and the coupling caps C11/12 and C13/14 if they are PIO but less likely is they are plastic film type such as the originally supplied "orange drops".

These things can be difficult without having the unit in front of us though, and bad joints are a common cause so go over it all carefully.

Also voltages are very often the indicator so do check them at switch on before it starts working correctly and compare the good channel to the bad.

[jiten]

Thank you Richard, I have measured all the voltages and they are all within 5% of the expected voltage.
I will repeat this to see if it shows up as an intermittent fault is so difficult to pick up.,
The capacitors you mention are the orange drop ones. I looked at Hifi collective. If I do replace the orange drops, what would be the equivalent or better type? Any particular manufacturer?

Best wishes, Jiten.

[Richard]

Hi Jiten, it's unlikely to be the orange drops if you have those then, as they are plastic film and very reliable.

I'd change the EL34 cathode bypass caps which do fail typically after around 10 years regular use and are easy enough to swap, C15,16,17,18, 100uF 63V or 100V rating and always a good insurance as if they fail they can do more damage.

It could also be a bad joint or resistor though so perhaps also take a multimeter to it and check as many as possible in situe. The fault condition seems to be when cold so it would be easy to work on and you may find one out of spec. Check also the earth wiring and joints and re-solder any suspect ones.

[jiten]

Hi, I repeated the standard voltage tests immediately after switch on and the voltages are very similar to yesterday. I will check the resistors but when I built it, I followed the advice that all connections should stand on their own and the solder should just secure them- so being obedient, made sure each wire was securely wrapped around the tags....BW, jiten.

[jiten]

All resistors check out! I will order some new capacitors and change the ones you suggest but am almost tempted to rebuild the tag boards with all new components.....the problem of course being that it might not solve anything if it is something off the tag board.
Have you any experience of the Hificollective? seems to have a wide range of components.
Best wishes, Jiten.

[Desmodromic]

Hi Jiten.

In my experience, HiFi Collective are very nice guys, very helpful, and they do amazingly fast delivery. I usually get my parts the next day!

Good luck.

[colin.hepburn]

Originally Posted by Desmodromic

Hi Jiten.

In my experience, HiFi Collective are very nice guys, very helpful, and they do amazingly fast delivery. I usually get my parts the next day!

Good luck.

yes HiFi Collective are very good

[jiten]

Thank you all. Kit 34 remains an enigma. everything seems ok so restarted it and perfect sound.....perhaps the threat of rebuilding it was enough to make it behave itself.
Will change the capacitors anyway. I suppose any component can behave in this odd way and the only way to deal with it is to change one thing at a time.
Another oddity is that all the 100k R1 to R4 resistors in the power circuit, the central tag board read 75k . R 5 reads 1.5K .Similarly the 560 K resistors in the right and left channel parts list actually read 420K on the tag board. Measured with the power off.
All the other resistors have the same value as the parts list.
Would the resistor values have been changed between the time that I built it and the parts list from a later date?
JT.

[Richard]

The erratic behaviour may be a failing electrolytic or a joint which warms up with use. I'd change all the electrolytics for good quality commercial ones. Some of these new caps do have very good specs such as low esr. I used Panasonic FCs recently (pennies from RS) for a complete re-cap of a pre and power amp and the result was way better than expected.

You may need axial types for some positions and if so the Vishay (BC) ones are excellent or the Rifas of course though they are more expensive and larger. I found it best to spend a few minutes first with a rule making notes of sizes and radial/axial from the amp. Then find suitable ones on the RS (or HFC) site.

Your resistors are all fine; the 100K are in parallel with 300K formed by the other resistors, R5 is 1.5K, and the 560K are in parallel with 1.83M formed by a string of other resistors.