Thorsten Phono Amp problem.

[Andrew]

Originally Posted by Tweeky

Hi Andrew,
The cliffcon pins are as follows:-
Pin 1 is 0V heater
Pin 2 is 250V HT
Pin 3 is 0V HT
Pin 4 is 6.3V heater

With the TL circuit totally disconnected, the Phono works fine and the voltages are:-
Pin 1 to earth = 43V
Pin 2 to earth = 263V
Pin 3 to earth = 0V
Pin 4 to earth = 49V
Pin 2 to pin 3 = 261V
Pin 4 to Pin 1 = 6.1V

Incidentally the 1st time I did the check, I hadn't replaced V2 in the WAD Phono and the Pin 2 to earth figure was 276V.

The resistance across pins 4 & 5 of the ECC88 is 7.4 ohms.

Thanks

Steve

OK, that makes sense. If we take this as relative to earth on the Cliffcon the voltages seem to be.

Pin 1 is 43v (heater -)
Pin 2 is your B+
Pin 3 is ground or 0v.
Pin 4 is 49v (heater +)

1 and 4 are the WAD raised heaters and the 88 checks out so wire up the heaters as above.

I would do this by taking a wire from Pin 1 Cliffcon to pin 9 on the 83 and a separate one from Pin 1 to pin 4 on the 88.

I would take a third wire from Pin 4 on the Cliffcon to pins 4 and 5 on the 83 and another to pin 5 on the 88. (Assuming I got that right...)

cheers,

-- Andrew

[Tweeky]

Hi Andrew.
I have done that, but took them off the psu output rather than the phono input so WAD Phono was totally disconnected. Still no glow from ecc88 heater. Anode voltage is 325V on pin 6 of the ecc88, pin7 is 170mV. Pins 4 & 5 are 3.1V & -2.9V.
Tried disconnecting HT circuit but still no heater glow.

Thanks
Steve

[Andrew]

Originally Posted by Tweeky

Hi Andrew.
I have done that, but took them off the psu output rather than the phono input so WAD Phono was totally disconnected. Still no glow from ecc88 heater. Anode voltage is 325V on pin 6 of the ecc88, pin7 is 170mV. Pins 4 & 5 are 3.1V & -2.9V.
Tried disconnecting HT circuit but still no heater glow.

Thanks
Steve

Hmmm....assuming nothing is wrong, which it obvioulsy is, then pin 4 and 5 on the 88 should be 43v and 49v relative to ground. That needs to be correct before we can connect the HT. I know this sounds odd, please don't connect up anthying but the heaters, forget the grid, the HT and cathode. Just focus on the heaters.

For the 88 alone there should be only be two wires in your circuit. Nothing else, to be sure I would remove it all. Wire Pin 1 Cliffcon to pin 4 on the 88 and pin 4 Cliffcon to pin 5 on the 88. Do the 88 first then the 83.

There should only be 4 wires in your new circuit and the heaters should fire.

cheers,

-- Andrew

[Tweeky]

Hi Andrew,
With just the heater power connected I'm getting +3.1 & -2.9V on both valves. Do you want me to disconnect all the other connections from the valve bases, and re-try?

Thanks

Steve

[Andrew]

Hi Steve,

Do they glow? The voltage still looks odd, should 43v and 49v (roughyl) are you measuring relative to Pin 3 on the Cliffcon?

cheers,

-- Andrew

[Tweeky]

Hi Andrew,
Relative to Pin 3 on the cliffcon, voltages are
ecc83 pin 4, 6.1V, pin 9, 0V
ecc88 pin 4, 6.1V, pin 5, 0V

The ecc83 glows, the ecc88 does not.

Thanks

Steve

[Andrew]

Hi Steve,

Still odd, the voltages on the valve heaters should be the same as the pins on the Clifcon were when you measured them. I think they were at 43 and 49 thereabouts.

This says to me you have a connection between heater- and the ground (could be pin 3) somewhere that should not be there.

Think of the heaters, pins 1 & 4, as a completely separate circuit from the HT, pins 2 & 3, of the Cliffcon.

We're looking for 43 and 49v on those heater before moving on and two nicely glowing valves.

Do you have a digi camera?

cheers,

-- Andrew

[Global]

You may have a 0 volt continuity problem between the PSU and the phono or you may be measuring WRT the wrong place. The heaters should certainly be elevated by 40-odd volts and according to what you say they are not.

However, since you DO have 6 volts across the heater pins of the ECC88, it should light. You need to check the valve itself. Remove ECC88 from circuit and measure resistance across heater pins. Open circuit=bad valve.

If this test OK you may have a bad connection between pins and socket.

Mark

[Tweeky]

Hi Andrew,
I have now disconnected every other connection from the valve bases and have the required 49/43V form the heater connections. However, the ecc88 valve is not glowing, but is not open circuit between pins 4 & 5. Resistance measures between 7 & 9 ohms. Very confused!

Thanks

Steve

[Clive]

Measure the current to the heater, should be 0.3A shouldn't it?

Could the the probelm have been caused by incorrect wiring on the 83? Should be Pin 9 to 0V and both pins 4 and 5 to 6.3V