Machine in shed for 15yrs - 1/4" audio tape PR99 Revox

Welcome to ETO!

carolmaille said:

On the back next to the socket I lowered the power to 140V from 220 and switched it on

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The selector on the back doesn't 'lower the power'; it selects the appropriate input for the mains voltage. If you set the selector for 140V, that's what the mains voltage should be. So applying 220V mains with the selector on 140V will destroy something. If you're lucky, only the fuse has blown.

Oh good, so the circuit selected was expecting 140V and it got 220V yes of course that makes sense now, I don't have a variable input, it is for a machine in different countries. Yes hopefully it is just the fuse ! I will get another one and get back here. Thank you so much

Older instrumentation have bulk caps in them, electrolytics, that can degrade over time.
And many with tantalums that essentially become shorts. Dipped tants very much a
restoration project to replace.

"Normally" one brings up these older instruments with a variac over some time, ramping
V over hours, a day or two, sometimes avoids damage thru cap reforming.


Regards, Dana.

That's good to know maybe I need to borrow a Variac as I would like to try to avoid replacing the dipped tants if possible

The variac will not help with the dipped tant problem. Just the electrolytics.

As a rule of thumb one just simply replaces the dipped tants, they are notorious for
failing as dead shorts.

I restore 90's era Tek scopes, 30 - 50 of those dipped tants to replace, tedious
to say the least.

That's okay as long as the track can hold - I just don't have a solder iron here but I am sure I can get one easily enough. Do you order them from RS or Farnell or something? And just lead solder. I can try to download a manual tomorrow and order them - and the electrolytics I guess. I also have a scope it seems to be dead - the tube - I guess it could be more capacitors !

Hello, so the machine is dead, having put 220V through the 140V selector so perhaps the transformer has blown, or the bridge rectifier? So would you say if I am ordering capacitors to order one of these as well ? I have a scope but not here with me at the moment.

carolmaille said:

order one of these as well ?

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Wouldn't cost much for a bridge rectifier, but the transformer could be a major expense. You really need to test suspect components before throwing money at buying new ones randomly.

Thank you I will at least open it up

If you've applied massively too much voltage (as it seems you have) the most common problem is just blowing the mains fuse, however, if you're unlucky (or the fuse has been replaced by a nail?) the transformer will blow. Parts on the secondary (bridge rectifier, capacitors etc.) have a fairly low probability of being damaged.

As you're presumably in Europe? (although it looks like you're using a VPN) then why did you turn it down to 140V?.

OK, I've downloaded the service manual, it looks a really nice machine - the mains fuse is on the back panel, so no need to take anything to pieces - just take the fuse out and check it. As 230V uses a smaller fuse than 120V, it's hopefully blown before any damage was done. I would suggest checking the fuse, replacing it with the correct type, making quadruply sure it's set to the correct mains voltage! - and try it again.

If the mains transformer has blown, you're pretty well stuffed, it's a very complicated multi-winding transformer, and even if available would cost a fortune.

Don't get too worried about capacitors, it's a 'relatively' new machine, all transistors and IC's - it's the old valve equipment where you tend to need to reform the electrolytics.

It's a nice looking machine, and odds are replacing the fuse (and checking the voltage setting yet again) will restore operation - mechanically it could be a different story, as belts, pulleys and pinch rollers deteriorate over time and lack of use.

Hello I have to say I am really lucky, I changed the fuse and it did not work but then I saw that the fuse had actually fused, again I think. So there are two fuses across transformer inputs I think and they are both fine. I changed the main fuse again, switched it on set to 220V and hurray! the LED display comes on, the tape deck button did respond the spindle turned slightly. I switched it off again right away. I am in the UK at the moment but I am resident in France it is true. Also I put it on 140V as I was thinking back to front that somehow the input would be reduced to 140V but of course it is adjusting the path of the current for 140V. Anyway now on the correct setting. Do I simply keep turning it on for short amounts of time? Someone said the electrolytic capacitors can rebuild ? I love hearing that it is a 'relatively ' new machine. It is a MkIII I can see on the back. I have a couple of reels so I ought in theory be able to lace it up and see if they turn. One of the heads looks a bit discoloured maybe that will alter with cleaning. Thanks

carolmaille said:

Hello I have to say I am really lucky, I changed the fuse and it did not work but then I saw that the fuse had actually fused, again I think. So there are two fuses across transformer inputs I think and they are both fine. I changed the main fuse again, switched it on set to 220V and hurray! the LED display comes on, the tape deck button did respond the spindle turned slightly. I switched it off again right away. I am in the UK at the moment but I am resident in France it is true. Also I put it on 140V as I was thinking back to front that somehow the input would be reduced to 140V but of course it is adjusting the path of the current for 140V. Anyway now on the correct setting. Do I simply keep turning it on for short amounts of time? Someone said the electrolytic capacitors can rebuild ? I love hearing that it is a 'relatively ' new machine. It is a MkIII I can see on the back. I have a couple of reels so I ought in theory be able to lace it up and see if they turn. One of the heads looks a bit discoloured maybe that will alter with cleaning. Thanks

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Capacitors are unlikely to be a problem, as it's not an antique valve set - where old ones can explode as they may need reforming first. There are no capacitors of that age in the Revox, nor the voltage levels to explode capacitors as in old valve equipment. Leave it on long enough to see if it works.

As you're in the UK set it to 240V, and back to 220V when you return to France.

Hi again
I will try that. A pinch roller has decomposed a bit - its very sticky - perhaps other rubber parts too. I will try wiping it gently - with 'white spirit' ? But I might need to find a substitute? I don't suppose I can drive it back to France - customs - duty - so I'll then leave it here til I get back

carolmaille said:

Hi again
I will try that. A pinch roller has decomposed a bit - its very sticky - perhaps other rubber parts too. I will try wiping it gently - with 'white spirit' ? But I might need to find a substitute? I don't suppose I can drive it back to France - customs - duty - so I'll then leave it here til I get back

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Replace the pinch roller, if it's sticky it's already too far gone - check any other rubber parts as well.

Back when I used to get tape recorders for repair it was VERY common for the rubber belts to have completely disintegrated, and disappeared all together - if you were lucky, you could find a faint dust trail to show where they went.

I did huge numbers of Philips and Grundig tape recorders, and plenty of Thorn and various BSR TD2 based ones (such as Fidelity - in fact, at one time, I owned two Fidelity TD2 based tape recorders I'd restored). I also did a few Ferrograph recorders, and Tandberg - I also bought a faulty Akai Stereo 7" reel to reel cheap - the guy selling it said the heads were duff, but the fault was an intermittent loud hissing noise?.

Turned out whoever told him the head was duff wasn't wrong, it was intermittently O/C, producing a loud frontend hissing noise when it went O/C. So I replaced the head (it was pretty costly!), and it was a great machine. However, I rarely used it, and eventually sold it.

Thinking back, I also had a Philips reel to reel, I got it for free as the customer just wanted it throwing away - and unusually it had an electrical fault. I'm repaired lots of similar era Philips machines, and the faults were always mechanical - in particular they had "rubber ju ju's" (that's what we always called them at work), three of them under each turntable, as a kind of clutch, you had to replace them, and shim the turn tables to the correct height. Anyway, I took the bottom off, looked around and spotted a single Wima capacitor (Wima were the most unreliable capacitors there were), so I changed it, turned the machine back over and tired it - cured!! So I serviced it, belts, rubber ju ju's etc. and swapped it for (I think?) a faulty small valve PA amplifier.

This was the start of my best ever swapping sequence, I started with nothing, never spent any money, and ended up eventually with a motorbike (a Triumph Tiger Cub).

Thank you what experience you have! Sorry to be so stupid but could you let me know where I could get the pinch roller from and other replacement parts ?

carolmaille said:

Thank you what experience you have! Sorry to be so stupid but could you let me know where I could get the pinch roller from and other replacement parts ?

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I've no idea, but presumably a google will find sources?

Here's presumably the official site?

Thanks. I have to find some speakers to see if there is an output but the FF and RW work - the and of course Play does not work because the pinch roller is sticking, but the buttons seem to be okay. The LED counter rotates with the reel motion so that's good. I need also to get some more reels these although they are working are a bit squashed and cracked. Its looking quite good

Revox made some of the best consumer reel to reel tape machines. Definitely worth restoring.

Good luck on your endeavors.

One word of advice; please seek a service manual. These machines have some quite elaborate mechanical assemblies.

schmitt trigger said:

Revox made some of the best consumer reel to reel tape machines. Definitely worth restoring.

Good luck on your endeavors.

One word of advice; please seek a service manual. These machines have some quite elaborate mechanical assemblies.

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It's freely available to download, a simple google finds it.