Tandberg 64x after changing capacitors

[Levente]

Hi Graham, i have measured it against the chassis...i will measure again against the negative rod of one of the caps...will updated in a bit..

[Levente]

New measures against the neg rod of one of the cap:

ECC81s
1: 87V 1: 136V
2: 0V 2: 0V
3: 2V 3: 0V
4: 12V 4: 12V
5: 25V 5: 25V
6: 72V 6: 69 V
7: 0V 7: 0V
8: 6V 8: 0V
9: 19V 9: 19V

ECC 82s

1: 42V 1: 0V
2: 0V 2: 0V
3: 1V 3: 1V
4: 13V 4: 0V
5: 25V 5: 26V
6: 192V 6: 197V
7: 6V 7: 6V
8: 31V 8: 30V
9: 20V 9: 19V


ECC83s

1: 130V 1: 122V 1: 123V 1: 3V (anodes)
2: 0V 2: 0V 2: 0V 2: 0V (grids)
3: 1V 3: 1V 3: 1V 3: 0V (cathodes)
4: 0V 4: 0V 4: 0V 4: 0V (heaters)
5: 12V 5: 12V 5: 13V 5: 13V (heaters)
6: 136V 6:126V 6: 91V 6: 3V (anodes)
7: 0V 7:0V 7: 0V 7: 3V (grids)
8: 1V 8:1V 8: 0V 8: 2V (cathodes)
9: 6V 9:6V 9: 0V 9: 7V (heater centre taps)



I have double checked the numbers of the pins to the printed out PCB schematic board..

[ms660]

It might help if you post the voltages with respect to the valve's circuit designation, Eg:

V1, V2, V3 etc.

Lawrence.

[Levente]

I have posted the measurements of where and which tubes on the PCB board.....still feeling like

[ms660]

Voltages aside, for anyone following this, the circuit designations for the valves on the playback amplifier board (1st thumbnail) are:

Top left = V6 (ECC83)
Top right = V5 (ECC83)
Bottom left = V8 (ECC82)
Bottom right = V7 (ECC82)

Circuit designations for the valves in the 2nd thumbnail are already given on the board.

Lawrence.

[Levente]

Thanks Lawrence

This is my first time dealing with such a machine..absolute beginner on tube gears..

are the readings suggests a resistor issue?

[ms660]

Not sure, not looked at the voltages yet but will do.

Lawrence.

[Station X]

I've added some electrode designations to post #42.

Let's concentrate on the ECC83's. One of these has very low anode voltages on pins 1 and pin 6.

Locate the resistors connected to these pins.

With power OFF measure these resistors using your meter on a suitable ohms range. (One meter lead to each end of the resistor). Compare this with the specified value. The valves can be in or out.

If the values are OK, apply power with the valves in and measure the voltage on BOTH ends of these resistors with respect to the capacitor you were using in post #42. Post the results here.

ECC83s

1: 130V 1: 122V 1: 123V 1: 3V (anodes)
2: 0V 2: 0V 2: 0V 2: 0V (grids)
3: 1V 3: 1V 3: 1V 3: 0V (cathodes)
4: 0V 4: 0V 4: 0V 4: 0V (heaters)
5: 12V 5: 12V 5: 13V 5: 13V (heaters)
6: 136V 6:126V 6: 91V 6: 3V (anodes)
7: 0V 7:0V 7: 0V 7: 3V (grids)
8: 1V 8:1V 8: 0V 8: 2V (cathodes)
9: 6V 9:6V 9: 0V 9: 7V (heater centre taps)

[ms660]

Ok...One board at a time, playback amplifier board (1st thumbnail in post#44)

The valve heater voltages don't make sense in the thumbnail, it's a series parallel arrangement for the heaters, V7 & V5 heaters are connected in series, V8 & V6 are also connected in series, those two series circuits are connected in parallel across the 25 volt DC heater supply.

Looking at the V7 & V5 series string, the heater supply voltage (25v +ve) comes in from point 26 on the board and goes to heater pin 5 of V7 where you've recorded a voltage of 26 volts (that's close enough) On heater pin 4 of V7 you've recorded a voltage of 0v, however, that heater pin is connected to heater pin 5 of V5 on which you have recorded a voltage of 13 volts, there's a discrepancy there.

To complete that series circuit, heater pin 4 of V5 connects to point 27 on the board (chassis/ground)

Looking at the V8 & V6 heater series string the voltages are more or less in the ball park, so should be no problem there.

So....Do all the valve heaters on that board glow when power is applied?

There are other voltages that are badly out on that board but first things first...Heaters.

This post might cross.

EDIT: Post crossed with Graham's.

Lawrence.

[Station X]

Lawrence.

We been here before as far as heater voltages are concerned.

Further up the thread in post #35, I had the OP check the voltages between pins 4 and 5 of every valve and he got around 12V.

Perhaps there's an intermittent fault, but we're going round in circles.

[Station X]

Low anode voltage is inconsistent with no heater voltage.

[hans]

Are the heaters on this machine AC? If you measure with DC then you get zero.

[Station X]

The heaters are fed from a 25V DC supply and are connected in series parallel combinations.

[ms660]

Originally Posted by Station X

We been here before as far as heater voltages are concerned.
Further up the thread in post #35, I had the OP check the voltages between pins 4 and 5 of every valve and he got around 12V.

No worries Graham, I was just pointing out the discrepancy recorded in Post#44's first thumbnail and trying to find out if all the valve heaters on that board were glowing at that point in time despite the voltage discrepancy recorded.

Lawrence.

[Levente]

Thanks for all your help guys... before I start and measure the resistors... could these symptoms be caused by a faulty ECC83? or definitely resistor...

[ms660]

Valve = less likely, resistor/capacitor/or a PCB short = more likely, carry out Graham's resistor test.

Lawrence.

[Levente]

Hi Graham,

Thank you for this. I have measured two resistors next the ecc83 which had no power nearly.

Power off:

R214 0,1 MOhm with power off measures 0.1018 mOhm /

Power on: Can't measure anything. My meter wont respond at all. Measuring against the neg rod of a cap.

R208 47kOhm wit power off measures 44.7kOhm

Power on: can not measure anything, no response of my voltmeter.

[Station X]

You probably have a disconnection in the PCB track leading from the resistors to the power supply rail.

[Levente]

I have checked the pcb and it seems okay..no loose pins or components. I have used a magnifier glass too to go through but i will double check it maybe I have missed something...any other components could be faulty? any other resistors? Thank you Graham....

[ms660]

Also R224/C214 ? Voltage check both ends of R224 with respect to ground (HT -ve)

Lawrence.