My Recovery Project. Sound Riviera TD2.

[Paulus.d]

Four weeks ago, I had a double heart bypass and a valve replaced. So I thought I'd get myself a little project to spend the three months recovery doing. I got a Sound Riviera TD2 based machine.

It still had a round pin plug on its mains cable... they haven't beeen used here for 40+ years. I cut it off and fitted a standard UK plug . The deck is completely jammed ...on stripping I've found the spool carriers were locked onto the pillars on the deck plate so tightly that the pillars worked loose and one came off.

I have sorted the mechanical side and got the deck running nicely now. On powering up , the tape plays back lovely but in record, it isn't erasing or recording anything. The Level tube is reacting to sound and you can hear a tiny bit from the speaker as I remember.

I've changed nothing electronically yet but it does have 2 yellow and black 50uf hunts caps fitted and the record contact switch looks as if it's been wet and corroded.

Paul

[Michael Maurice]

I’m glad to see that you’re on the mend.

I would replace the switch if you can, then look at then if it still doesn’t record, check the bias oscillator

[mickm3for]

Hi sounds like the bias/erase osc in not running, should have a sinewave across the erase head in record mode Mick

[Paulus.d]

I don't have any fancy test equipment....only a multimeter
paul

[Michael Maurice]

You should be able to measure something on the AC range of a multimeter.

[DMcMahon]

If the Magic Eye valve is a EM84 then I think the correct schematic will be for the Sound A41, if the Magic Eye valve is EM87 then the correct schematic I think will be the Sound A41A, both of these schematics (in the service information) are downloadable/purchasable from the Instant Downloads at top right of screen.

The service information indicates that the Bias Oscillator signal is around 50kHz and somewhere around 20 to 30 volts at the Erase and PB/Record heads in Record mode.

To measure with any accuracy you will need an oscilloscope (converting the peak to peak waveform voltage to rms) or a VTVM or electronic/FET voltmeter.

A basic voltmeter may read some voltage although a cheap voltmeter may cause the bias signal to collapse.

If you read no voltage/low voltage then try cleaning the record contact and making sure with resistance/continuity measurement that there is low resistance/good continuity across the record contact.

David

[DMcMahon]

My references above to "record contact" should have read "record contacts".

David

[Paulus.d]

Metered across erase head during record - no voltage, checked continuity between head and contacts on record switch checked out.
There are two nasty looking wax caps 0.0005uf across the bias coil... they're a bit wet? sloppy?? like the wax is melted..
Paul

[Paulus.d]

got the service data - Paul

[DMcMahon]

Did you mean 0.005uF (5nF/5,000pF) ?

The A41A schematic shows 5nF (C13) across the bias oscillator coil and 5nF (C12) going to one end of the coil.

The A41 schematic is similar with 4,700pF across the coil and 0.005uF going to one end, the A41 schematic does not give component number designations.

Wax capacitors can look messy even when they are good/serviceable, in this case because of their age I would renew them, both for future reliability and to remove them out of the fault finding scenario.

David

[Boulevardier]

Hope your post-op recovery goes from strength to strength.

Worst-case scenario with the Sound is open-circuit winding(s) on oscillator coil or erase head (probably unrepairable unless you can find salvaged replacements). Easy to check those (with power disconnected) with a meter. But study the circuit to ensure that you don't need to disconnect other components in parallel with the windings to get a meaningful meter reading.

I agree that the capacitors are prime suspects in a power oscillator circuit that's 60-ish years old, but sensible to check these windings as it's easy, and until you're sure they're OK you may be wasting your time replacing capacitors.

Mike

[knobtwiddler]

Originally Posted by Paulus.d

I don't have any fancy test equipment....only a multimeter
paul

If you are having a few weeks away from the daily grindstone, then I would've thought this to be a great period to learn how to use a scope and oscillator. You don't need more than 20MHz for analogue audio work, and if you are shrewd, you can find Japanese scopes by the likes of Kenwood / Trio or Hitachi on Ebay for well under a hundred quid. Likewise for oscillators. When it comes to debugging a reel machine a scope will show you all sorts of things that a MM will not. 80s Japanese scopes (or German Hamegs) go on pretty much indefinitely, so don't be put off by age. Best wishes for the recuperation!

[Boulevardier]

I should have added that you may not want to test the heads with a multimeter if you don't have access to a head demagnetiser, as the current passed through the head by a resistance measurement can leave the head magnetised and this will put some hiss on your tapes (including ones already recorded and just being played). If you have a demagnetiser, it's easy to avoid this.


Mike

[DMcMahon]

Using a digital meter as opposed to an analogue meter should reduce the risk of magnetising the heads.

David

[Paulus.d]

Stupid me ... removed the record switch to clean the contacts , which went really well but a small cap marked 820 was soldered across the pins ......I've forgotten where it was fitted

Paul

[DMcMahon]

First rule of any disassembly work, electrical and mechanical is to take lots of photos, take notes and sketches as required before disturbing anything.

Looking at the A41 schematic it shows a 820p (820pF) capacitor across contacts 9 & 7 of the Playback/Record switch, so I assume this must be the capacitor in question.

So using your test meter to check continuity/resistance you need to check the switch connections to the schematic to work out where the capacitor should connect.

First identify the common contact 8, this connects back to the common junction of the two 0.05uF capacitors and the 100k and 470k resistors.

Then identify contact 9 which will have a 220k resistor connected to it, the other end of the 220k resistor connects to pin 3 of the ECC83 valve. The 820pF capacitor should connect to pin 9 together with the end of the 220k and the other end of the 820pF should connect to contact 7.

You will see on the schematic that it shows the switch switched across contacts 7 & 8, this is the Playback position, when switched to Record, the common contact 8 should switch across to contact 9.

David

[Paulus.d]

thank you ... i know , my stupidity - Paul

[DMcMahon]

If you confirm the type of Magic Eye valve fitted it will help to confirm correct schematic.

In Post 1 you referenced two 50uF capacitors, I can only see one in the A41 & A41A schematics.

David

[JohnBHanson]

If this has an AMP/SUP button (grey on the lhs near the on/off tone control) then make sure this is not pressed. If pressed during record it turns of the erase current (superimpose mode).

[Paulus.d]

No ….. it doesn’t have the button there . Also it has the EM84 record indicator
Paul