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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 29th Nov 2022, 8:08 pm   #1
DMcMahon
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Default Truvox PD-95 R2R Check Out

Brought this very recently, appears to be in quite good condition for its age but needs a good spring clean. Fairly large, heavy and sturdy machine.

Early 1960's vintage, 4 track, 3 speed (3 motors), max 7" spools, mono valve recorder with no internal speaker or power amp.

Selling faults listed were :-

1. No sound on playback.
2. Fast wind in both directions struggles when tape loaded.
3. Tape counter not working.
4. Tape pressure pad falling apart.

Tried to remove the chassis from the wooden case but unable to on first attempt, seemed to be catching something in bottom left corner. Two of the SST securing screws were partly seized but got them out eventually. Also two of the control knobs were stuck solid on their control shafts, the red one for On/Off & speed control when it did eventually come off, it took off like a rocket, it is somewhere in my garage buried under loads of equipment, will have to locate it later.

Removed hardboard rear panel and hoovered out lots of cobwebs and dust. Found remnants of tape counter belt (actually looked more like a rubber band). The counter works when its pulley is rotated so a replacement belt should get it working, it needs to be a long belt.

After replacing the 13 amp fuse in the mains plug with a 1 amp, powered up slowly, all OK. The mains on lamp (on Control Panel) does not work, this is powered from the valve heater supply from the mains transformer, this supply measures OK at 6.8V, not able to get to the lamp without removing the control panel, at this stage assume the lamp has blown.

Play mechanically works well on all 3 speeds. Fast wind in both directions often works well with positive and fast operation. Occasionally for no obvious reason fast wind will not start at all in one or both directions. Impossible to see from the front or rear what is not working, assume that the relevant reel motor is not moving. Hopefully when the chassis is removed from the wooden case it will be possible to see more. Removal of the capstan motor & reel motors assembly sounds quite major.

Connecting headphones to the Output socket (this is also parallel wired off to the Output phono on the side panel) on the front control panel and with the volume control (VOL 1) set to maximum, can hear a very quiet playback. Touching the PB/Record head wires does induce a hum signal that is somewhat louder than the playback signal but not particularly loud.

Main HT voltage at reservoir capacitor C26 is OK at 325V (schematic shows 350V). HT2 at first filter C25 is 312V, HT3 at second filter C21 is 301V, HT4 at C9 is 245V, HT5 at C1 is 180V. C21/C25/C26 is the red Plessey triple can, dated 1963.

Pre-amp valve electrode voltages all appear good, no +ve voltage getting to the Control grids and no obvious paper capacitors.

David
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Last edited by DMcMahon; 29th Nov 2022 at 8:16 pm.
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Old 29th Nov 2022, 10:15 pm   #2
Analogue man
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Default Re: Truvox PD-95 R2R Check Out

I always liked these machines; they seemed very well built and usually reliable. I just wish they had made one which would take 10.5-inch reels.
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Old 29th Nov 2022, 10:32 pm   #3
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Default Re: Truvox PD-95 R2R Check Out

I once owned a transistorized version of this deck (R102?). The problems I had with the audio were due to duff electrolytic capacitors. I recall it being a difficult machine to gain access to! That was 30 years ago now.
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Old 30th Nov 2022, 7:43 am   #4
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Default Re: Truvox PD-95 R2R Check Out

The reason they did not develop a 10-1/2" deck was two-fold: 1) their major commercial market was the educational field that did not require 10-1/2" and 2) that they were handicapped by their superb, sculptured cast-alloy deck; so they concentrated on top of the range domestic decks, amps... and speakers. Unlike Brenells, Collaros (and BSR) the deck could not be expanded to fit a larger spool.

When Truvox and Thermionic Products (later Racal-Thermionics) airfield and data recorders merged, domestic audio took second stage but the superb 100/200 lent itself to a professional 7" field data-recorder, the Racal-Thermionics T3000 now with a 4-th speed 15ips... but still only 7" spool!

Truvoxes have always been underrated, but the 100/200 was as good as any domestic Brenell, Ferrograph, Grundig....
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Old 30th Nov 2022, 10:21 am   #5
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Default Re: Truvox PD-95 R2R Check Out

I should have mentioned that the PD-95 is one of numerous Series 90 models.

David
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Old 30th Nov 2022, 2:36 pm   #6
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Default Re: Truvox PD-95 R2R Check Out

Did a quick recording test using an old Grundig microphone that I have never used before.

Got a good recording signal on the recording level VU meter and could hear/monitor a good signal on headphones, but on playback of the recording just got total silence.

Because the VU meter gave good signal and could hear the record signal indicates that the record amplifier has some reasonable life and because the same circuitry (with different switching etc) is used for the playback amplifier, the playback amplifier probably is OK.

Do not yet know if Erase works, next need to check out the record bias and erase signals, the switched connections to the Play/Record head and the head itself.

The record level VU meter is the type where the meter needle sits at max reading (+3 red) on the right hand side of the meter and when switched to record the needle moves over towards the left side and then a zero set rotary control can be adjusted for meter reading of zero (0% / -20 on this meter).

First time hands on with this type of record level meter, have seen them before on machines like Ferrograph 4/5/6 Series.

David
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Old 2nd Dec 2022, 9:18 pm   #7
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Default Re: Truvox PD-95 R2R Check Out

Erase also does not work.

Play/record head windings appear good, 1049 Ohms / 867mH & 1056 Ohms / 860mH, have seen no data for these heads but think they must be OK.

While doing other tests fast rewind became erratic, previously it generally worked well with occasional failure to start but now it was failing to start regularly.

Decided to try and remove the chassis again from the wooden case and was successful on this second attempt. As expected, the reel motor (Garrard) shafts do couple direct to the reel tables so as long as the reel table brakes are removed (they are) then the reel tables should spin when the respective motor drives in fast wind.

With chassis out of case then easy to access the mains on lamp, it was black so looked blown, disconnecting one wire to isolate the transformer winding gave an open circuit reading across the lamp. Tried to remove the lamp from the lamp holder but impossible to remove, so cut off the holder and threw away. Used a 6 volt wired grain of wheat type lamp as replacement.

Removed the Take Up reel table in order to install a replacement tape counter belt (counter is driven from the take up reel table), was not easy to access the small hex head grub screw that locked the reel table to the motor shaft.

After searching through loads of drive belts could not find one long enough and small enough thickness to fit in counter pulley correctly. Tried a 1.9 x 120 but far too tight and stopped the Take Up table rotating in Play. Also tried a 2.5 x 145 but this also too tight and too fat really for the pulley.

Tried stretching a couple of other belts to try and make fit but they both broke during stretching, looks like will need to purchase a suitable belt.

The two 2uF motor run capacitors measured OK, 2002nF / 0.33 Ohm ESR & 20008nF / 0.16 Ohms ESR, did not voltage check them.

The 2 motor resistors measured OK, 3000 Ohm measured 2.97kOhm & 4000 Ohm measured 4.02kOhm

David
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Old 3rd Dec 2022, 12:49 am   #8
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Default Re: Truvox PD-95 R2R Check Out

For counter belts, I just cut up and glue O rings. Especially handy when access is difficult, you can glue it in situ after threading!
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Old 3rd Dec 2022, 9:50 am   #9
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Default Re: Truvox PD-95 R2R Check Out

Thank you Ben, I will try that. I have glued belts a couple of times before and they did not last very long before coming apart but they were thicker non counter belts.

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Old 3rd Dec 2022, 9:57 am   #10
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Default Re: Truvox PD-95 R2R Check Out

Make the cleanest cut possible, tiny drop of superglue, shove'em together and hold for a minute...job's a good 'un!
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Old 3rd Dec 2022, 10:41 am   #11
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Default Re: Truvox PD-95 R2R Check Out

Not seen one of these PD95s - I have a couple of the R-92s. Electronically they were OK, mechanically the grease on the brake system had solidified. Also the motor run capacitors were well out of spec. Really nicely made as all Truvox products (with a couple of notable exceptions!) were.

Just wondering what the PD signifies? It looks like a less well-specced version of the R92/94. It couldn't just be a playback machine, could it?
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Old 3rd Dec 2022, 2:03 pm   #12
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Default Re: Truvox PD-95 R2R Check Out

Quote:
Originally Posted by brenellic2000 View Post

When Truvox and Thermionic Products (later Racal-Thermionics) airfield and data recorders merged, domestic audio took second stage but the superb 100/200 lent itself to a professional 7" field data-recorder, the Racal-Thermionics T3000 now with a 4-th speed 15ips... but still only 7" spool!
Barry in the Series 90 Service Manual, the company name has been amended to "Kaytronics Ltd. (formerly Truvox Ltd.)".

I may well have missed it, but I cannot remember reading this in your "A Truvox Product" book.

David
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Old 3rd Dec 2022, 2:06 pm   #13
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Default Re: Truvox PD-95 R2R Check Out

I was also wondering Glyn if the PD stands for anything.

Definitely a Playback and Record machine.

David
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Old 3rd Dec 2022, 3:23 pm   #14
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Default Re: Truvox PD-95 R2R Check Out

I have now found Kaytronics Ltd in the Truvox book, it was listed in the index as on page 54.

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Old 3rd Dec 2022, 3:33 pm   #15
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Default Re: Truvox PD-95 R2R Check Out

I see from the Series 90 schematic and motor wiring diagram that the capstan motor run capacitor is shown as 2uF and run capacitor for the reel motors is shown as 2.7uF

Both on my PD-95 are 2uF, on my PD-99 the capstan motor is 2uF and the reel motors is 2.7uF (so the PD-99 matches the schematic).

So it looks like the reel motor run capacitor on the PD-95 is incorrect value, maybe it has been previously replaced or maybe originally built with incorrect value, the capacitor is the same Plessey capacitor as the other 2uFs

Whether this will make any difference to the fast wind performance, I am unsure.

David
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