Another Advance E2 thread.

[humphrey]

I have had this piece of kit for a long time now and it has never worked with no output.
I changed all the visible resistors apart from some low value ones that seemed ok. It has an ECC91 instead of ECC82. The Hunts caps are still present and all the E caps have been changed plus all the waxy ones.
I was hoping to be able to set up my Serviscope Minor.
Any suggestions?

[Station X]

Start by measuring the HT voltage?

[humphrey]

The ht is 377vdc and 290vac from the transformer.

[Station X]

That sounds rather high.

How do the other voltages compare with the circuit? In particular the cathode voltages which will show whether the V2 is conducting.

Is the AF signal present at the socket?

[humphrey]

You have the same schematic that I have but the C15 + goes directly to pin 8.
The mod switch is either cw ext or int. Which should it be?
There is no AF signal.

[Electronpusher0]

Quick word of warning, the manual posted in #4 has a redrawn schematic. It shows the oscillator valve as ECC82 HOWEVER the pin numbers still refer to the ECC91 which is different.
The ECC91 has a common cathode and in the E2 the grids and anodes are also connected accross so the two triodes act in parallel.
I have just got mine working and it was remarkably in Cal.
I changed the 'orrible 'unts and several of the high value resistors were way out of value. As was the Cathode resistor of the AF section.

Peter

[Electronpusher0]

Originally Posted by humphrey

You have the same schematic that I have but the C15 + goes directly to pin 8.
The mod switch is either cw ext or int. Which should it be?
There is no AF signal.

If you want to test the AF oscillator you have to select "mod" or the oscillator is disabled. In fact the AF osc valve then becomes an amplifier for the ext mod.

Peter

[ms660]

Also on that schematic the heater pin numbers for the 6SN7GT are wrong, should be pins 7 and 8.

Lawrence

[Station X]

Originally Posted by humphrey

You have the same schematic that I have but the C15 + goes directly to pin 8.

Is R31 still present and R10 of the correct value?

Originally Posted by humphrey

The mod switch is either cw ext or int. Which should it be? There is no AF signal.

That's been answered in a previous post, but details can be found in note 3.6 of the service info.

[humphrey]

The mod switch has two settings - CW EXT Or INT

[humphrey]

R10 is corret (1K) but r31 is missing - but that is how it was.

[Station X]

Originally Posted by humphrey

The mod switch has two settings - CW EXT Or INT

I refer you to my previous answer. To check the AF output the switch needs to be in the INT position and R12 wound up.

[humphrey]

Originally Posted by Station X

I refer you to my previous answer. To check the AF output the switch needs to be in the INT position and R!2 wound up.

OK done.

[humphrey]

V3 pin 8 is now 340 vdc
V2 pin2 is now 322 vdc pin 3 is 14v pin 6 is 90v

[Electronpusher0]

Originally Posted by Electronpusher0

If you want to test the AF oscillator you have to select "mod" or the oscillator is disabled. In fact the AF osc valve then becomes an amplifier for the ext mod.

Peter

Thank you for the correction in post 12 Graham, I of course meant "INT"

Peter

[humphrey]

I put the ecc91 on the Taylor 45C and did the usual turning A to the X and B to zero. Pressed the meter button and had the needle go full scale and trembling. Is that a bad sign? abc 770 and 2 13 0

[WME_bill]

another advance e2 thread.
This looks like a valve tester query, even though the ECC91 is the oscillator valve used in Advance signal Generators.
As a Valve testing query, no. it does not sound right. Either the valve is failed or the Tester is failed, or operating voltages and the base connections are set up wrongly.
I have just checked, and the base connections for each half of the double triode look correct. So suspect your 45C Valve Tester.
wme_bill

**********Moderators please consider if this does not belong with a Signal Generators thread. ************ But to a Taylor 45C Valve Tester.

[Station X]

I'll leave your useful post where it is Bill, but let's not turn this into a thread about the OP's valve tester.

Everyone has their own way of tackling a repair job, but pesonally I'd concentrate on getting the AF Oscillator working before moving on to the RF oscillator.

Does the mode switch have continuity? Does T2 have continuity?

[humphrey]

I checked the T2 and the mod switch and all is well there.

[WME_bill]

Advance E2 AF output.
I had no AF on my E2 and found it was the 0.05 capacitor C12 across the coil T2.
It must have been so lossy that the oscillator would not start. When replaced, it oscillated and I found that the other waxey C13 0.05 was leaky, so I replaced that also.

R11, 2.7M resistor which sets signal level to the modulator had gone high. It worked, but not the 30% I expected using my oscilloscope.

It is an ingenious circuit. In the Ext-CW setting, the oscillator is stopped by removing the feedback from anode pin2 to the grid pin1 so that that half of the 6SN7 (p 1,2,3) acts as an amplifier, anode load R8 100k, and Va 170V.

As an Oscillator, T2 is a Hartley coil, lower end to grid p1 through the 0.05 capacitor C13. anode p2 the top end, and HT feed via S2A to the tapping, about 1/3rd up from the bottom grid end.
The modulator in both CW-Ext and Int settings is the other half of 6SN7 on pins 4,5,6, fed via S2B from R10-EXTernal input or INT from anode of oscillator via C13.

The HT voltages are being quoted. On my E2, the HT rail to pin5/top of smoothing capacitor C14 16uf was 380V on CW /355V on INT, with 1v pk ripple. The anode of the oscillator section pin2 is 375V on CW and 342V on INT. Cathode pin3 was 6.6V on CW and 24V on INT. The HT to the RF oscillator valve 6J6 pin1&2 is around 105V dropping on the higher frequency bands to 80V.
Oscillator AF output at max (on INT) was about 140V peak,giving 50v rms as in the specification..
wme_bill