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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 26th Feb 2021, 4:23 am   #1
Techman
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Default Truvox R1 (Model RE-15)

I was given this tape recorder yesterday. It came complete with a Grundig TK20 and had obviously been stored somewhere a bit damp for a number of years. The previous owner hadn't had it for very long having obtained it locally from Facebook market place. It didn't have its original mains lead, but he bodged a mains connection to its two pin inlet and had powered it up. He said that things seemed to be working with a low hum from the speaker, but no sound. He told me that as he was pushing the buttons and winding the tape there was a 'bang' and a cloud of smoke that stank the room out. He switched it off quick, but told me that after a short break he switched it back on again and the tape transport was working, but still with no sound other than a low level hum from the speaker. He then opened it up and thought he could see a wax capacitor with the end blown out, also two valves that had gone to air with the usual white on the inside top of the glass. Last week he had phoned me to ask my advice on a possible repair and he was going to let me know the numbers of the two 'gone to air' valves when he had another look at it later that week. However yesterday he phoned me and asked me if I was doing much and that if I wasn't, did I want to come and collect a couple of tape recorders as he just wanted rid of them out of the way, so off I went to collect them.

Having got it (them) home and opened it up, the first valve to notice that had gone to air was a 6BW6. I found a spare 6BW6 with the numbers rubbed off in my valve stash, with a '6' still just visible and I could tell by the innards that it was the correct valve. The second valve to have gone to air is right within the middle of the guts of the machine and looks a bit of a swine to get at, so I haven't tried to get to that one yet. I could see the capacitor that had exploded and again, it looked to be in an awkward position behind the transformer and likely connected across the mains input. I decided at this stage to fit the replacement 6BW6 and apply mains and see what the state of play was. I could see the heaters of the rectifier and the EL84 valves glowing, but the replacement valve wasn't. At this stage I decided to check the heater continuity of the replacement valve, and it was good and agreed resistance wise with the original valve, also just to verify that there was nothing silly going on with the replacement valve, I powered its heater via the bench power supply and it glowed normally, but not in the valve base on the machine. I checked for heater voltage at the valve base and it was as it should be. The base is quite corroded and even after cleaning there was still no results. Even moving the valve about from side to side makes no heater connection, so the valve base has had it and needs to be replaced. I suspect that there was originally a bad (hot) connection on one or both of the heater pins in that base, which eventually caused a hair line crack in the glass around the pins causing the valve to go to air - I've come across this same type of fault a number of times in the past. I think this valve type may possibly be a bit prone to this, being a larger valve (6V6) in a much smaller bottle.

So that was that. He'd mentioned to me last week that the pinch roller was also in a bad way, being perished and with a large flat from being left engaged with the capstan for probably the last 60 odd years...and it was pretty bad when I got to see it. I'm glad he didn't, in the end, ask me to try to repair this tape recorder for him, as it would have been a pain in the backside to try to do anything with and I'd have had to probably tell him that it really was beyond economical repair. I think he hopes that I'll be able to do something with it and perhaps get it going well enough to play a tape rather than scrap it, but he is a realist when it comes to these things and won't be too bothered if I tell him it turned out to be a lost cause. I haven't completely given up on it at this stage and I'm going to take the innards and the case outside later today and give them a good blow out with the air blower to get rid of all the built up dust and muck that's accumulated over the years and then go from there. It's not worth spending a lot of time on, but it's an interesting artefact from its time - a few pictures of it below and in the following post:-
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Old 26th Feb 2021, 4:28 am   #2
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Default Re: Truvox R1 (Model RE-15)

A few more pictures showing the bad valve and its corroded base, the blown out capacitor down in the guts and the perished and grooved pinch roller:-
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Old 26th Feb 2021, 12:45 pm   #3
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Default Re: Truvox R1 (Model RE-15)

A nice looking recorder, a shame it has got into a bit of a state corrosion wise inside, certainly plenty to sort out, could be a good project for you.

David
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Old 26th Feb 2021, 1:03 pm   #4
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Default Re: Truvox R1 (Model RE-15)

Is there a recording level indicator somewhere ?

David
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Old 26th Feb 2021, 1:46 pm   #5
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Default Re: Truvox R1 (Model RE-15)

The “rubberware” on those old Truvoxes was always a problem waiting to happen. When moved around in storage, the spring-loaded arm carrying the capstan roller would always end up in the play position - with the roller pressed against the capstan shaft. You will probably find that the motor spindle has done the same damage to the rubber tyre on the flywheel.

Mike
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Old 26th Feb 2021, 2:55 pm   #6
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Default Re: Truvox R1 (Model RE-15)

The level indicator is an inset magic eye on the front left hand side of the speaker and unbelievably it has a bulb that lights up the whole surround - you'd think that the last thing you'd need with a green indicator valve would be a bright white light shining all around it! On the right hand side of the speaker is a big red Truvox emblem - you'd think that this would have the 'power on' indicator lamp behind it, but this area is covered behind by the frame of the enormous elliptical speaker.

It's outside at the moment having had its blow out and removal of all dust and creature remains. The carrying handle is on the rear of the cabinet, the bolts of which form part of the case fixing to the chassis, so when the machine is not in use it stands face down, so if on a dirty damp floor the front tends to get a bit marked.

I agree that the play mechanism is very light and it takes little effort for that large lever to engage the pinch roller, so I can see how these units can end up being left in storage with the roller engaged. The rubber tyre on the flywheel shows some light cracking to its surface, I haven't noticed a 'flat', although I've not looked that thoroughly at it as yet.

It's an extremely heavy machine for its size, one of the heaviest that I've come across, I think. I'll get a picture of that magic eye surround lit up later when I bring it inside and apply power once again - it's rather bright!
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Old 26th Feb 2021, 10:53 pm   #7
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Default Re: Truvox R1 (Model RE-15)

It's not as bad to work on as I first thought. A couple of bolts and another couple of nuts and washers and the deck top can be separated from the chassis. The other valve was an ECC83 that had gone to air with a bent pin 4 and a crack running from it. Fitting another valve produced no heater glow (should have checked it before fitting it). However, on removing it I found that its pin 4 was now bent, so that's another bad valve base socket - luckily this valve survived and the pin was straightened. I thought I may as well straighten the pin on the old cracked valve and use it to try to get the valve base socket to line up, but it caused the glass to crack even more and bent the pin once again. The pin sockets must be badly corroded and partially disintegrating, so really to be right, probably all the valve sockets need replacing for reliability, whether this is worth the trouble is another matter - perhaps a project for some time when there's time! In one of the photos below you can actually see corrosion to the inner plate of the valve, showing that it's been cracked for an extremely long time and moisture has actually got inside the glass from damp storage at some point.

There were two wax capacitors across the mains input at the transformer, one of which was still in tact, so I cut them both out, leaving the ends of the wires so that I'd remember where they were for some time in the future. I've got a feeling that the magic eye may have also gone to air as it's got a funny look about it and there's no sign of life from it. The smoothing capacitors seem good with no sign of warming and the HT is around 270 volts - there's a date on one of June 57.

I removed a bit of the flat spot from the pinch roller and the tape transport does work, but the roller would really need refurbishing or replacement - there doesn't seem to be any flat spots on the flywheel tyre. Although the card says Model R1, the plate on the machine says Model RE-15 - the serial number on the machine agrees with the one written on the card. The "glue on lid" written in chalk on the inside bottom of the case is strange!

So there we have it - more pictures below:-
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Old 27th Feb 2021, 8:21 pm   #8
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Default Re: Truvox R1 (Model RE-15)

It turns out that the magic eye is alright after all - see picture which is unfortunately a bit out of focus. So the recorder needs a couple of valve bases, a couple of valves, a pinch roller and a mains lead with the correct two pin socket plug - see picture. The valve bases are fixed with nuts and bolts and I do have some of the correct type spare. The show stopper is the pinch roller, although I may have something that I can adapt. The rubber of the pinch roller is rock solid and was just rotating until the flat spot met the capstan shaft where it stopped. Having rubbed the flat spot down it does now rotate with the capstan, albeit slightly bumpy, but once a tape is installed, it doesn't grip and won't rotate with the capstan, as its rubber surface is so solid and hard that the thickness of the tape stands it off from gripping the capstan. There's ways round this that I can bodge to make it work, so we'll have to see. The speaker cone and voice coil seems to be free to move, which isn't always the case when something's been stored in the damp as this machine has. The whole front of the machine seems to be a casting - no wonder it's heavy! The deck top is Formica topped plywood with a metal clad underside with cast deck top top fittings. I've put the machine back together for the time being until I decide what to do with it and when.
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Old 27th Feb 2021, 8:44 pm   #9
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Default Re: Truvox R1 (Model RE-15)

Just a couple of other points from my own experience with this deck for your future reference..

You've probably worked out that the deck has DC braking through the spool motors. If it's the same as my Mk III, it gets that DC from the amplifier HT supply. I found that a nuisance (and didn't feel it a good idea to subject my Mullard 5-10's HT line to the strain) and just connected a small silicon power rectifier between the 240V AC mains connection and the braking circuit feed on the switchbank - which worked fine for the years that I had the deck.

The other issue I had was that the plywood deck warped quite badly from the heat of a 5-10 beneath it (they were both in the same case). Maybe I didn't give it enough ventilation, though, thinking back, there seemed to be plenty of space and airflow.

Good luck with your search for a pressure-roller!

Mike
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Old 28th Feb 2021, 8:52 pm   #10
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Default Re: Truvox R1 (Model RE-15)

Thanks for that, Mike. Yes, it's a clever idea with the DC braking of the motors. I gather that the decks alone were used in other setups - the Mullard 5-10 amplifier with a couple of EL84s would generate a fair bit more heat than the single EL84 in this machine, although it's surprising that it warped with the metal cladding on the underside of the ply, mine fortunately still seems to be dead flat.

The chap I got the recorder from gets these machines mainly just to see what possible interesting recordings may be left on the old tapes. He told me that there was nothing interesting on the tape which came with this machine, and he was right. I played various parts of the tape on another machine and it was all classical music, which sounded from the background crackle all the way through that it had been recorded from 78s, probably 12 inch classical album sets of the time. The bits that I played were seamless with no stops and clicks between records, so the pinch roller disengage pause lever was used with great effect by the operator. The condition of the early Scotch tape is very good and the recordings were actually not that bad, other than an awful recorded on mains hum throughout both sides of the tape, so the base control had to be turned to minimum to make it listenable. I don't think that this hum was a fault of the recorder at the time when the recordings were made, but rather from a lack of screening or earthing of the interconnections of the recording set up being used. I suspect that the tape with this machine, which has both identical Scotch spools is probably the original and only tape that was ever used with it and it may well be that it had very little use before it was put away and forgotten about. A machine that's had a lot of use generally has odd spools from playing a collection of many tapes, whereas this machine has identical spools from the tape that was probably sold with it originally. The other recorder that came with this one, a TK20, actually works to a degree and has a tape of a football match on it - he warned me about this and gave me a quick demonstration of it before I took it, although you never know, it could be a classic recording of a rare match!

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