PSU11/Phono11 - voltage drop

[NickG]

Looks to me as if something if pulling the heater voltage up when the phono is connected, I would check that with the power supply disconnected, there is no conduction between the heaters and the rest of the circuit. Maybe a valve has shorted the heater to cathode. The voltage would make me think it may be the final cathode follower, as the other cathodes are near 0v. Try with the final valve removed.

Also check the voltage divider resistor, and joints on the elevated heater supply.

[Black Stuart]

Hi all,
it is impossible to describe the self bollocking that could be heard over at least half of Guadix - guess who soldered an HT wire to a heater pad and what makes it worse is that I did the self same thing when I originally built Phono11 GRRRRRRRRRRRRRRRRRRRRRRRRR.

I've calmed down now - well a little. With an 18K at R6 in PSU11, I'm getting 252/3V (250V) at T/P 3 & 6 in Phono11 now, so that objective has been acheived.

In Phono11, I've got 3 T/P readings that are too high; T/P 2 V3, pin1, anode 120V (95V) this is high but just about acceptable: T/P 5 V2 pin1, anode 199V (95V) this is very high but both of these could well be influenced by T/P 7 V3 0.87V (1V) and T/P 10 V2 0.001V (1V) and T/P 4 V4 pin8 cathode 200V (95V). I will probably remove the Tants I have in R27/28 for the supplied RS carbons. I shall use the s/iron on the valve sockets and see what happens.

I made series values for R23/24 - 316K & R25/26 - 39.2K and they have drifted (Tantalums) apart from all the extra solder used, I feel that maybe it is better to use (1) resistor rather than 3 - does anyone have a single 316K 1/4 W resistor going spare?

Embarrassed of Guadix

[buddam]

Stuart

I'm ordering some 316K from Richard (see for sale/wanted). Better for postage that I get it and include with Percy tube coolers I'll be sending to you (haven't yet decided on purchase but will get back to you possibly tonight).

I did test readings last night. Will post later when home from work. I think my 95V has always been up near 120V and was again last night.

Adrian

[Black Stuart]

Hi Adrian,
I'd love to get a single 316K, I must have lost one of the pair that came with Phono11.

I reckon you need 3 tube coolers per tube. The Pearl Coolers are good but the carbon fibre jackets can easily unravel and I see no need for them, so I'd like at least 18. Actually they won't cool the signal valves but will kill any or most microphonics and this is a real problem with signal valves.

The Pearl Coolers for power valves are good and really do help to cool and therefore lengthen the lives of the valves - these don't use the carbon fibre jackets by the way.

If you have PSU11 and the voltage is high into Phono11 do change R6 for an 18K 5W wirewound - if you don't have any I can send you one, Greg kindly sent me 2 and lol I had 5 I did'nt know about.

I'm going to do the RIAA mod and either myself or Nick is going to put in an order from THL in Taiwan for some Rikens etc, let me know if your interested. In fact have a good look at their site www.thlaudio.com. They are a first class co. to do business with - whatever you fancy, e-mail them and they will e-mail back prices.

Tonight I feel the need for a rest re. Phono11 - so it's a glass or two of wine and the h/amp for me.

Black Stuart

[buddam]

Hi Stuart

I am interested in the Rikens - I'll sort an order out in the next 24 hours. On the tube dampers, are you referring to the stabilisers/dampers at $5 for 10 or something more exotic? On the 18K 5W resistor, are your spares Mills? Ceramics are awful in comparison I've found. Waiting to find tolerance of the 316K resistors, but I think Welwyn 55s are 1%

Best

adrian

[Black Stuart]

Hi all,
could those that have Phono11 please measure T/P 2 & 5. It should be 95V but I've never had that kind of reading and now Adrian has chipped in with his comment. Are R27/28 of influence here because even though I tested all resistors before rebuilding Phono11 R27 is virtually 'dead' at 0.001v, T/P 5 is 200V (95V): R28 is 0.87V (1) and T/P 2 is 120V. R33, T/P 4 is 199V (120V). There seems to be a clear correlation with the voltages I am getting via R27/28/33, which are all directly coupled to the three valves, so it may well mean re-soldering the valve bases but I just wonder if the first two readings are also something to do with the resistor values at R27/28?

I have also mentioned on another thread that all the 1/2W resistors have drifted, whilst 1W hav'nt - food for thought here.

Black Stuart

[Black Stuart]

OK,
I now have a functional Phono11. I removed the existing R27/28 and used 2 more Tants 2.2K here. I used more solder on the anode pins of V3/V2 and the cathode pin of V4. Bar two slighty high T/P readings at 2 & 5 all the rest are very good.

I don't like the series resistors for R23/24 - 316K or R25/26 - 39.2K, it's a lot of solder and I wonder if anybody has used Roderstein Resista rs - they are metal film, not carbon. They are available in the exact values needed - any opinions?

Black Stuart

[buddam]

Stuart

by coincidence I used 39K for the pseudo shunt mod on my 50K panasonic pot. For various reasons I no longer used them. I have 2 Rikens and 2 Kiwames @ 39K. If you can live without the 0.2K you'd be missing I can send 2 of your choice at some stage

Adrian

[Black Stuart]

Hi Adrian,
I feel that the exact value is important here - perhaps a 'wise one' could comment here.

Black Stuart