Hacker Cavalier Loud Noise

[Nickthedentist]

Originally Posted by Edward Huggins

If you've cleaned them with, say, an emery cloth and sprayed the pins and the holders with Servisol, dipping them will make no real difference except to waste your fluid.

I agree. But I prefer to dip the pins rather than spray the holders as I find it less messy and wasteful. I keep a tiny jam jar with 1/2" of Servisol Super 10 in it for exactly this purpose, and it only needs topping up occasionally.

[martinpinner]

It has been suggested on several occasions that the problem might be the valves and having not found a solution I am assuming that this is the only option now open to me to get a fix for the problem. If you are of the opinion that the valves are not the problem then I will with the forums help continue to search for a solution. Thanks.

[Nickthedentist]

I wonder if there is a member local to you who could try your valves in one of their sets to prove whether or not they're responsible.

[peter_sol]

Strange that there is zero volts on pin 2 of both valves as if the valves are drawing current there should be 2 or so volts.
Martin, if you look at the circuit diagram, see post No. 40 you can check your wiring
Start from the chassis line (bottom horizontal line on circuit) and go upwards towards each of the pin two's
You can compare your physical wiring with the circuit.
You may have a connection to the earth line by mistake.
Yes it is still likely that the noises were and are being caused by the valves.
The PCL86 and ECl86 were quite troublesome valves in that respect, as those of us who worked on TV sets will remember.

[martinpinner]

Thanks I will check the wiring and test the voltage again as it is a small value. I will let you know what I find when I have done.

[martinpinner]

Tested the voltage again on pin 2. On one valve I get 1.3V and 0V on the other. Checked wiring and it is OK. I have just removed valves again and will clean again before I refit.

[peter_sol]

Does the amplifier work now?
because you should not have zero on one of the cathodes.

[Station X]

Originally Posted by martinpinner

Tested the voltage again on pin 2. On one valve I get 1.3V and 0V on the other. Checked wiring and it is OK. I have just removed valves again and will clean again before I refit.

Swop the valves over and see if the fault ie 0V on pin 2 is associated with the valve holder or the valve.

[Station X]

If the fault is specific to a valve holder rather than a valve it would help us if we knew which valve holder exhibited the problem.

Check the voltage across R8 2.2k (seventh pair of tags from the left) and R4 2.2k (second pair of tags from the right).

[martinpinner]

Will swap valves and check resistors. Once done I will let you know.

[martinpinner]

Here are the results of valve swapping.
Valve Socket 1 Valve Socket 2
Valve1 Valve2 Valve 2 Valve 1

Pin 1 0 0 0 0 Grid of Triode.
Pin 2 1.3 1.3 0 0 Cathode of Triode.
Pin 3 265 266 265 265 Screen Grid of Pentode.
Pin 6 291 290 270 270 Anode of Pentode.
Pin 7 7.64 7.92 7.65 7.56 Cathode of Pentode.
Pin 8 0 0 0 0 Control Grid of Pentode.
Pin 9 123 126 0 0 Anode of triode.

What I noticed whilst taking the readings was that at no point during the first readings of the pins with valve 1 in socket 1 and valve 2 in socket 2 did the noise kick in. However when valve 2 was in socket 1 and valve 1 in socket 2 the noise kicked in whilst getting readings.

R8 reads 2.17K OK. R4 no reading although this is a new resistor.Will have to replace. Also tested R3 at this time and could not get a reading this time. I will have to get a replacement resistor.Any assistance is appreciated.

[Station X]

Please don't use the expression "No reading". It's meaningless. Use "Short circuit" or "Open Circuit".

[Lucien Nunes]

There is no voltage on one of the triode anodes (pin 9), but there is on the other. This means either R6 or R7 is open-circuit, dry jointed or fitted incorrectly. It also explains the missing voltage from the cathode of that valve (pin 2). Turn off power, allow time for HT to completely dissipate and trace with meter on resistance.

It is extremely rare for resistors to just go open-circuit, unless they are visibly burnt out due to a fault elsewhere in the circuit (and none of the suspect resistors could easily burn out in this circuit). I suspect dry joints or damage to the resistors during installation. As a guide, I have probably fitted 1000 resistors since I had a problem with one. You should not normally expect to have to replace them!

[martinpinner]

Thanks checked R6 and R7 and these read OK. R6 needs resoldering.

[Station X]

R6, R7 and R8 are testing OK, but the soldering may leave something to be desired (to paraphrase your own words).

Doubt hangs over R3, R4 and R5. I cannot believe so many resistors can be faulty. There's something wrong with your measurements or you still have wiring errors.

[peter_sol]

You are getting there Martin and learning.
The reason the noise is there in one socket and not the other is because the first valve in the chain will be more sensitive
You really need a new valve.

[martinpinner]

I will check again.R3 is difficult to see and get probes on easily. I will remove the capacitors and then take a reading.

[martinpinner]

If replacing valves. Is it correct that you have to purchase a matching pair.

[Station X]

Originally Posted by martinpinner

I will check again.R3 is difficult to see and get probes on easily. I will remove the capacitors and then take a reading.

It would be much easier to measure from pin 1 of the valveholder to chassis. That way you'll test the wiring too.

[martinpinner]

Thanks for that.