Simon Minstrelle

[DMcMahon]

Have been having a quick look at my latest acquisition, a 1960 Simon Minstrelle, a 2 track single speed, mono valve reel to reel recorder.

It was sold as not working, so am not expecting too much, as expected it looks old and tired, one of its little legs is missing and the other three are about to fall off, there is also a missing control knob.

It uses a Garrard deck with Garrard Magazine tape system and can also use standard tape spools up to 4".

I thought its thin mains cable may have been 2 core (one of my pet hates) but opening up the 3 pin plug it is 3 core, with the usual 13 amp fuse fitted (a real pet hate of mine) so fitted a 2 amp fuse (normally fit 1 amp but have run out of them).

First port of call will be a thorough visual inspection of everything inside including checking the coupling capacitors.

[DMcMahon]

An example of one (4 track stereo version) in good condition

[DMcMahon]

After a bit of a struggle have removed it out of its case.

[DMcMahon]

Found that one of the +ve (yellow) legs of reservoir capacitor C27 (2 x 32uF) was not connected, think it goes on one of the legs of the bias oscillator L1 but not sure which one yet. L1 also was loose, a piece of its plastic body has broken away, I think the brass screw (somewhat loose) is the frequency adjustment slug.

Red connection leg of C27 has been cut to enable a better/easier measurement.

[Edward Huggins]

--Wow, 7 valves in this. No cost cutting here. What is the valve line up?

[DMcMahon]

Glue repaired the broken L1 mounting and worked out which one of its 4 terminals C27 connects to.

Started checking the various paper coupling capacitors. Difficult to remove them for meggering as their leads are tightly wrapped around terminal tags often with 2 or more other components wrapped around the same tag. So only practical way is cut them off but that leaves the leads too short to resolder without soldering on extension leads.

Replaced ERO capacitors C16 (0.04uF) & C19 (0.1uF) that couple the V5a triode output & the V2b Pentode output to the Pentode push pull output valves V3/V4. They did not measure bad as such but easier just to use new capacitors.

Replaced Hunts capacitor C13 (0.5uF) that de-couples the screen grid of V2b (ECL83) because it was very leaky (less than 50kohm at 50V on Megger).

Powered up slowly from Variac all OK. Main HT voltage good at around 275V volts (AC mains ripple not yet checked). Intermittently getting crackles on the speaker even with volume fully down.

Checked tape transport, Wind (Fast Forward) initially worked well, there is no Rewind on this Garrard deck. Play does not work, capstan shaft does not rotate, think I could hear the capstan motor rotating (but difficult to see it).

The capstan shaft is driven by a flywheel but I cannot see what should drive the flywheel, I assume a drive belt (unless direct drive) but no obvious sign of a belt.

While rechecking Wind operation, it suddenly stopped working, quickly followed by the internal mains fuse blowing (0.5A), AC mains current drain previous to this was around 0.22A

So need to remove the tape deck (looks awkward) to investigate further. Will probably power the deck and the rest of the unit as 2 separate units and keep an eye on current drains.

[DMcMahon]

Originally Posted by Edward Huggins

--Wow, 7 valves in this. No cost cutting here. What is the valve line up?

Yes quite a lot for a small recorder, the attached page 2 from the Service manual lists them.

David

[DMcMahon]

A big thank you to Terry (terry123) who has emailed me the service manual (very detailed) for the Garrard Magazine Tape Deck.

A quick look at this shows that there is no drive belt and the capstan flywheel is driven by the capstan motor pulley via an intermediate rubber idler wheel.

[terry123]

You are most welcome.


Reg Simon headed a most innovative little firm in a highly competitive market and engaged well known industrial designers of the day such as Peter Bell & Lucas Mellinger. I don't know if either were involved in the quirky design of the Minstrelle. The Garrard "Magazine" deck was ahead of its time but not taken up by many manufacturers or supported by the public. For this reason machines using this deck are rare. The Simon "Cymbal" launched in 1960 also featured the Garrard magazine. With one notable exception, the only makers to incorporate the Garrard deck were small concerns such as Simon. I have always like this particular one, decent amp and a built in mic to boot!

[DMcMahon]

For the one that is in the British Museum, the attached leaflet does state that Peter Bell was the designer.

David

[barretter]

The V&A is not the BM!

[DMcMahon]

Removed the tape deck, quite tricky had to unsolder various wires off the Play/Record switch and remove 2 switch wafers off the switch shaft.

Can see that if the motor runs the motor coupling should rotate the rubber intermediate idler wheel but there is quite a large gap (at least 2mm) between the idler wheel and the flywheel.

The idler wheel is sprung loaded but if the wheel is pushed against the spring, the wheel moves closer to the flywheel but then no longer makes contact with the motor pulley, so a bit of a mystery at the moment.

Tomorrow will power it up and see what happens.

[DMcMahon]

Originally Posted by barretter

The V&A is not the BM!

Yes silly mistake !

David

[unitelex]

Originally Posted by DMcMahon

Removed the tape deck, quite tricky had to unsolder various wires off the Play/Record switch and remove 2 switch wafers off the switch shaft.

Can see that if the motor runs the motor coupling should rotate the rubber intermediate idler wheel but there is quite a large gap (at least 2mm) between the idler wheel and the flywheel.

The idler wheel is sprung loaded but if the wheel is pushed against the spring, the wheel moves closer to the flywheel but then no longer makes contact with the motor pulley, so a bit of a mystery at the moment.

Tomorrow will power it up and see what happens.

Usually/sometimes the idler wheel is not only on a spring it is also on a pivot arm, allowing extension (spring) and some swing via the pivot. This allows it to move sufficiently to engage with both motor pinion and flywheel. If the pivot is seized it could explain the symptom you described. You might need to remove the idler to get to the pivot.
Best Regards
Chris

[DMcMahon]

Thank you Chris, that makes a lot of sense, I will have a proper look tomorrow.

David

[DMcMahon]

Chris was spot on the money. The idler wheel pivot arm assembly is seized solid on its mounting shaft.

Have not been able to free it using WD40 and gentle persuasion, will remove the motors assembly to get better access to be able to work on it more.

[unitelex]

Originally Posted by DMcMahon

Chris was spot on the money. The idler wheel pivot arm assembly is seized solid on its mounting shaft.

Have not been able to free it using WD40 and gentle persuasion, will remove the motors assembly to get better access to be able to work on it more.

Localised heat from a blue flame, done with care, (removal or shielding vulnerable parts from heat) is usually effective at freeing seized plain bearings from my experience. Obviously not a method to use if there is any plastic or fibre bushes/washers etc in the pivot assy. Lube after cooling.

[DMcMahon]

I had considered trying heat but thought better of it as rubber resilient mounts for the motor frame nearby.

With motors pulled back out of the way, it was fairly easily to remove the pivot arm assembly, clean and lubricate, mechanically is working well now and driving the flywheel when motor manually turned.

When the motors were lifted away, found that the 6 mounting bolts for the top mounting frame of the motor assembly were all loose due to the rubber resilient mounts (2 per bolt) all starting to turn to goo and decomposing.

Attached photo shows one of the bolts that I was able to remove, to remove most of the others would probably require a big strip down as very difficult to access and hold the cheese head bolts at the lower end to be able to undo the top end to strip them down.

With it all bolted back together the movement on the rubber mounts is not so bad but if the rest of the unit comes good I would plan to fit new mounts, tap washers would do a good job I think.

Next I will try powering up the tape deck, first need to find a replacement 500mA 1.25" fuse.

David

[Edward Huggins]

Originally Posted by DMcMahon

Yes quite a lot for a small recorder, the attached page 2 from the Service manual lists them.

David

Many thanks for sight of this. Well, that's a really interesting circuit then. ECL83s used in a non-audio role and triode connected push-pull EL84s in a small tape recorder. Whoever heard of that before!?

[DMcMahon]

Have not yet powered up the tape deck chassis to test the motors as got side tracked checking out the main chassis.

The Garrard tape deck manual sates that in Fast Wind operation the motor current will be around 290mA. From previous main chassis tests know that the chassis is drawing around 220mA (in the static condition) so 220 + 290 = 510mA so possibly this is why the 500mA fuse previously blew.

Did a batch of tests on the main chassis to see if any particular area drawing excess current, but found nothing untoward, nominal 220mA seems to be the static running current.

Checked the various circuit voltages to the schematic, all basically correct.

Mental note to myself - Still to check AC mains voltage ripple on HT lines.

Replaced one more ERO paper capacitor that was a little leaky C14 (0.1uF) coupling capacitor to the EM84 magic eye.

Replaced electrolytic C12 (25uF) V2b cathode de-coupler as it measured very high capacitance (ESR was OK).

Spent quite a bit of time looking at V3 EL84 one half of the push pull output stage, its control grid voltage increases from a normal low voltage to around +12 volts over several minutes. Thought this seemed abnormal but not able to find a reason. Its cathode voltage is around twice the value shown on the schematic (20 volts as opposed to 10.5) . The cathode electrolytic de-coupler C20 (50uF) is only rated at 12 volts.

Schematic indicates that some models may have 100uF/25 volt C20 fitted.

So replaced C20 by two NOS 50uF/30 volt in parallel. No change to the cathode voltage or the grid voltage.

One apparent strange thing is that the the control grid (G1) wiring connections connect to pin 1 of both of the EL84 V3 & V4 output pentodes, the schematic valve base diagram indicates that pin 1 is internal connection (IC) and pin 2 is the Control Grid but nothing wired to pin 2 ?

Most of the resistors read higher than than their stated values, some outside their tolerance window but none bad enough to warrant replacing currently.