Hmv 2208

[Dorian27]

I have hmv2208 and I was listening to my tape on it and put it on the following night and absolutely no sound at all not even a crackel I have a spare set of valves changed those still the same no hum nothing at all all the vales glow nicely can any one please direct me to what it might be if I touch the cable on the play head no hum nothing at all I don't know where to look next any help would be appreciated

[ms660]

Service manual, voltage checks.

Lawrence.

[dazzlevision]

My initial checks would be:

Is there HT?

Is the speaker coil intact and are the two push-on wires to its terminal still on and making good contact?

I have had the primary winding of the audio output transformer go open ciruit on one of these models.

[Dorian27]

How do I check the HT please speaker ok wires connection to speaker ok and how to I check audio output transformer please

[dazzlevision]

You will need a test meter to check/measure the HT voltage (direct current).

To check the audio output transformer, you will need a test meter that measures Ohms (resistance). Alternatively, just measure the dc voltage on either side of the primary winding, which should have a high dc voltage on both ends. If one end is zero, or virtually so, then the winding is open circuit (faulty).

Do you have access to a test meter (often called a multimeter)?

Have you measured the resistance of the speaker’s voice coil (with one of the wires going to it unplugged)?

[Dorian27]

Yes I have a multimeter

[dazzlevision]

OK, make the measurements and let us know how you get on. The HT voltage should be present on at least one side of the audio output transformer’s primary winding. When testing for HT, set the multimeter range to dc volts (at least 250V range) and connect the negative terminal of the meter to the metal chassis of the recorder. Apologies if you know these basics already.

[Dorian27]

What sort of reading should I expect please

[Dorian27]

Ok thank you I will go to it at the weekend and let you know what readings I get thanks again

[dazzlevision]

The HT will be around 200 to 240 volts dc. The resistance of the speaker coil will be around 2 to 3 Ohms.

You will need to unplug one of the speaker leads before taking the measurement, as the audio output transformer’s secondary winding would otherwise give you a misleading Ohms value.

[dazzlevision]

Originally Posted by dazzlevision

The HT will be around 200 to 240 volts dc.

Here is a photo of the Audio OutPut Transformer (AOPT) - it is the much smaller of the two transformers in the photo and you'll see there is a small brown coloured capacitor connected between the two inner solder tags. These two tags are the primary winding of the AOPT. If the AOPT circuit is working normally, there will be full HT (around 260V) on one of these two terminals and a somewhat lower voltage on the other (around 245V). The terminal with HT on it is the one with the screened cable connected to it.

You will need to have the tape recorder switched on whilst measuring the HT voltage, so be very careful - the solder tags on the nearby mains transformer will have mains voltage on some of them!

If you have the recorder working when upside down, you will probably hear a mechanical scraping noise, as the recorder is not designed to work in this position, so have the recorder upright, with the speaker grille facing down.

If you're not sure you know what you're doing and you don't have suitable test leads with your multimeter (to avoid causing a short-circuit between two terminals), then I would leave well alone.

[Techman]

Not wishing to confuse the OP, but it's probably worth relating a true story of something that happened to me at the latter end of last year when working on someones similar tape recorder, so I would strongly advise checking the speaker first.

The tape recorder was brought to me with the complaint of no audio. I was measuring around the anode circuitry of the output valve with a DVM when suddenly it seemed to read an over voltage error, even though I knew the HT voltage wasn't more than 250 volts and the meter was on the 600 volt DC range. Stupidly I put the probe back on for a second go and blew the meter into the next decade - totally fried! I think I actually spotted the slight spark as it happened. I realised almost instantly what had happened, as due to an open circuit speaker, high induced voltages of probably several thousand volts were being produced by the unloaded inductance of the output transformer. This is exactly why a valve amplifier should never be run without a speaker load as the induced voltages can sometimes break down the transformer insulation and cause tracking in surrounding circuitry etc. My excuse for not realising that the speaker was o/c in the first place was that motor noise, transformer hum and the fact that I had a radio on at the same time, lead to the fact that I couldn't hear that it was actually totally dead. An o/c speaker is actually the last thing that you would expect on something like this - lesson learned, but I lost my favourite meter. It was only one of those cheap yellow ones, but I'd had it for a long time and I still haven't got over the loss of it yet! Another thing that didn't help as regards to amplified pulse voltages around the unloaded output stage was that once the speaker had been repaired, there was also found to be a very noisy valve base back down the line in the pre-amp section of the circuit.

[dazzlevision]

Originally Posted by Techman

Not wishing to confuse the OP, but it's probably worth relating a true story of something that happened to me at the latter end of last year when working on someones similar tape recorder, so I would strongly advise checking the speaker first.

I completely agree with you and checking the speaker for open circuit is the first thing I would do (and it can be done with the recorder disconnected from the mains).

The resistance of the speaker coil will be around 2 to 3 Ohms and one of the wires connected to the speaker's two terminals MUST be disconnected before taking the measurement, as the audio output transformer’s secondary winding would otherwise give a misleading Ohms value.

I hope that "Dorian27" follows this advice.

[Dorian27]

Hi I have tested the speaker coil and I get 3ohm I then tested output transformer as you told me and I only get 9v on one terminal and 10 on the other I have taken picture of transformer for you to see that I have the correct one thanks for your help much appreciated

[dazzlevision]

Originally Posted by Dorian27

I then tested output transformer as you told me and I only get 9v on one terminal and 10 on the other I have taken picture of transformer for you to see that I have the correct one thanks for your help much appreciated

OK, the black capacitor in your photo is wired across the primary winding of the AOPT and you should measure (one at a time) the dc voltage between each one of these terminals and the recorder's metal chassis.

Are you sure that your test meter is working correctly and is set on its DC voltage range?

Did you measure between the recorder's chassis and each terminal? To check you meter, measure the voltage of a 9V battery, using the same settings. If your meter is a digital one, you should still get a reading, even though the battery's voltage is much lower than the HT voltage on your tape recorder.

If you are sure your meter is working correctly and set to the correct voltage measuring range and connected correctly, then the very low voltage could be due to the following causes:

1. Something is excessively loading the HT voltage, dragging it down, but if it really is as low as 10 Volts, then I would expect something to be getting rather hot and distressed - any sign or smell of this?

2. The ac voltage on the mains transformer winding that feeds the HT rectifier could be very low. This would have to be measured. As you have the valve heaters alight, the 240V ac mains supply must be reaching the mains transformer's primary winding. Is the small lamp next to the record level indicator meter alight?

3. The HT rectifier is faulty. This is usually a small bridge "metal rectifier" made by Westinghouse Brake & Signal Company, with a "W" logo on it. It is screwed to the chassis, by the two transformers and has four terminals.

[Dorian27]

Yes the small light on the meter is working I have received checked voltage on audio transformer and they are between 10v I used another meter I had same reading how do I check the rectifier please

[Dorian27]

Yes I see the rectifier it has a w logo and FC.444 on I take that as part no

[dazzlevision]

I attach a photo of the Westinghouse FC444 bridge rectifier.

The two connections from the mains transformer are marked with a "S" and so they will have an ac voltage between the two. It will be around 230 Volts AC.

The other two terminals will be the rectified AC output and are marked with a "+" and a "-". The dc voltage between these two terminals should be around 250 to 260 Volts DC.

I advise you to switch the recorder OFF whilst connecting your test meter and be careful to avoid any short-circuits between the four terminals and the metal part of the bridge rectifier's outer case or the metal chassis of the recorder.

[Dorian27]

Do I test using black meter lead to chassis and live to test each individual please

[dazzlevision]

Originally Posted by Dorian27

Do I test using black meter lead to chassis and live to test each individual please

No, as I said in my post, you have to measure the voltage between the ac terminal pair ("S") and then the voltage between the two dc terminals (+ and -). When you measure the DC terminals voltage, you need to get the test leads connected correctly (meter + to FC444 + and meter - to FC444 -). For the AC test, it doesn't matter.