Tandberg TD20A-SE Repair and Restoration - UK Vintage Radio Repair and Restoration Discussion Forum

andrewferguson · 1st Jun 2022, 8:12 pm

A few weeks ago I got a Tandberg TD20A-SE. I got it for not much (mainly swapping some other kit for it) and the main reason for that was because it is in completely untested / "as-is" condition. I don't think it has been used for many years, and a visual inspection shows it to be in fairly rough shape, with the most noticeable issue being that one of the reel spindles is loose and wobbles around. (Whether this can be fixed, or a new motor is needed, I don't yet know.)

This will be the first time I've worked on something of this scale before. I suspect this thread will span many posts over a long period of time (unless I get stuck or discover a irreparable fault, which I hope doesn't happen!). I haven't yet powered it up (although I believe it was powered up a few weeks before I got it), in case I should try powering it up "gently", or checking the internals first.

From looking online, these seem to be well-regarded machines sound-wise, but also known to be prone to faults and issues. (I can see already that my machine is affected by the common issue of the Power / Speed / Tape Size latching buttons breaking). Given the condition my machine is currently in, I am expecting a fairly involved and lengthy repair.

So I guess my first question is.... what do I do first? Should I try powering it on? (If so, anything special I should do to power it on gently?) Or would it be better to start with a visual inspection of the internals (likely involving several photos posted to the forum with the question of "does this look OK?"

).

Andrew

Uncle Bulgaria · 1st Jun 2022, 9:10 pm

Turning it on is always a bad idea, and is always the most tempting. If it doesn't work, you're likely to make it worse, possibly frying some irreplaceable part, and if it does it's not going to be working well so you're going to be taking it apart anyway - it's going to be due a recommissioning service after such a long time out of circulation!

A visual inspection will throw up likely problems. I'm going to guess the usual suspects of capacitors, belts and resistors.

Do you have a service manual? I've attached the one I found at ElektroTanya.

As a ham-fisted amateur, I refer to the attached document a lot: "Steps to first powering on old equipment".

ben · 1st Jun 2022, 9:20 pm

The above document seems to refer to valve kit with things like wax capacitors, not late 70s solid state gear that has likely seen use fairly recently.

I have been working on 1970s Tandberg kit like this for decades and never had to take any special precautions.

My usual procedure is to power it up as normal, for two or three minutes, using all my senses (hot/smoky smells, wisps of smoke, odd noises, etc). Anything suspicious, be prepared to yank the plug right away.

Power off, look again, then power on again for longer.

Unless this unit has Rifa caps as mains or switch suppressors (which some Tandberg kit of this era has) then you needn't do any 'preventive replacement', like many US forums have as some kind of golden rule among their less technical posters. Indeed, you'll likely just introduce other problems.

You already have a loose spool table, you could look at sorting that out first. The you will be able to thread a junk tape and check for other problems.

Uncle Bulgaria · 1st Jun 2022, 9:34 pm

You're quite right Ben, I should have qualified the somewhat zealous tone of the doc in capacitor replacement! I have had a lot of trouble with Frako and tantalum bead capacitors in late '70s gear, so I'm just cautious now.

Ted Kendall · 1st Jun 2022, 11:30 pm

If it's been powered up recently anyway, I'd suck it and see. Rifas apart, I would expect anything spectacular.

andrewferguson · 2nd Jun 2022, 9:21 pm

Thanks all for your help so far. I powered on the machine today and there were no pops or bangs. After some testing (none of it involving a reel of tape yet), I have now confirmed a number of issues:

The capstan does not spin.
The pinch roller arm is very slow to move when play is engaged.
The three left-hand-side buttons (power, speed and reel size) are broken, requiring them be held in to work.
The left reel table is broken (snapped plastic) and the right is cracking.

The service manual is fantastic in detailing how to take apart and service these machines (really a step-by-step "for dummies" guide) and I have been following closely so far. Oh, and the little cartoon drawings contained within are fun too!

I have taken the front top cover off, and it was immediately obvious why the capstan wasn't spinning - the belt had broken. Additionally, the belt for the tape counter is very loose, so could do with replacing. Looking on ebay, there are a few sellers that sell a "belt kit" for this machine, but the cost is quite prohibitive (not helped by all these sellers being US-based) - the total cost including postage comes to over £30.

A much cheaper solution would be to get a generic belt that would fit. I've measured my belt and it is 345mm long and 5mm wide. This gives a diameter of 110mm, but I suspect by belt has stretched a bit with age, so if I ordered one I'd need to reduce the diameter a bit.

I don't suppose anyone here knows the dimensions of the original capstan belt this machine needs? (Sadly the service manual does not say.) Ditto for the tape counter belt (a square one that I haven't looked at yet, since it will require a bit more patience to remove).

Many thanks again for the help so far!

ben · 2nd Jun 2022, 9:37 pm

Look at this video just before the 1min mark. The pinch is activated by a worm gear, there will likely be hardened grease there. Do not keep using it till this is cleaned off as it may place undue stress on the gear teeth.

ricard · 2nd Jun 2022, 9:38 pm

A number of sellers on the German ebay site list a belt set for the TD20A ('belt' in German is 'Riemen'), although the cost is about the same, being EUR 20,- for the belts and EUR 10,- for postage (at least to Sweden, might be different to the UK I guess).

Not having any experience with this particular model, I would think a generic belt would work. Normally one would figure the length of an unstretched belt (i.e. measured with a piece of string for instance) minus 5 to 10 per cent.

andrewferguson · 4th Jun 2022, 3:54 pm

I've found an ebay seller that has 5mm belts of varying sizes. My (snapped) belt has a diameter of 110mm, the available sizes are 110mm, 106mm, 103mm, 100mm, 97mm, 94mm and 88mm (and smaller sizes but I suspect anything below 88mm will be really too small).

Not having much experience with estimating belt sizes (usually I order a kit for a particular machine, or have belts on hand I can try and see), has anyone got a rough idea of what belt I should pick? Right now I'm erring towards the 94mm one, but I don't want it to be too tight.

I've also looked out what grease I have for re-greasing the worm gear. The type I have on hand is "Castrol LM" grease (see attached picture). Is this suitable or is there a particular type that members here would recommend?

ben · 4th Jun 2022, 4:56 pm

You need lighter grease than that. I use CRC lithium-EP white grease which has served me well in general mechanical situations. In applications like this you only need a light smear.

As for belts, I'd go for the 110mm. From what I've read this seems the size. Is yours the high speed ( top speed:15 ips) or low speed (7 1/2) version?

andrewferguson · 4th Jun 2022, 5:33 pm

Quote:

Originally Posted by ben

You need lighter grease than that. I use CRC lithium-EP white grease which has served me well in general mechanical situations. In applications like this you only need a light smear.

Great, thanks for the advice. I'll pick up a can of "WD-40 Specialist High Performance White Lithium Grease" when I'm next in Halfords (I trust Halfords more for this sort of thing than some generic brand I could get today on ebay).

Quote:

Originally Posted by ben

As for belts, I'd go for the 110mm. From what I've read this seems the size. Is yours the high speed ( top speed:15 ips) or low speed (7 1/2) version?

Mine is the low-speed (3.75 and 7.5) version. Do you have a service manual that indicates the correct lengths?

Ted Kendall · 4th Jun 2022, 6:20 pm

Quote:

Originally Posted by andrewferguson

I've also looked out what grease I have for re-greasing the worm gear. The type I have on hand is "Castrol LM" grease (see attached picture). Is this suitable or is there a particular type that members here would recommend?

Superlube.

Michael Maurice · 4th Jun 2022, 7:33 pm

Quote:

Originally Posted by Ted Kendall

Superlube.

+1 I dont use anything else.

1st Jun 2022, 8:12 pm	#1
andrewferguson Hexode Join Date: Aug 2016 Location: Edinburgh, Scotland, UK. Posts: 262	Tandberg TD20A-SE Repair and Restoration A few weeks ago I got a Tandberg TD20A-SE. I got it for not much (mainly swapping some other kit for it) and the main reason for that was because it is in completely untested / "as-is" condition. I don't think it has been used for many years, and a visual inspection shows it to be in fairly rough shape, with the most noticeable issue being that one of the reel spindles is loose and wobbles around. (Whether this can be fixed, or a new motor is needed, I don't yet know.) This will be the first time I've worked on something of this scale before. I suspect this thread will span many posts over a long period of time (unless I get stuck or discover a irreparable fault, which I hope doesn't happen!). I haven't yet powered it up (although I believe it was powered up a few weeks before I got it), in case I should try powering it up "gently", or checking the internals first. From looking online, these seem to be well-regarded machines sound-wise, but also known to be prone to faults and issues. (I can see already that my machine is affected by the common issue of the Power / Speed / Tape Size latching buttons breaking). Given the condition my machine is currently in, I am expecting a fairly involved and lengthy repair. So I guess my first question is.... what do I do first? Should I try powering it on? (If so, anything special I should do to power it on gently?) Or would it be better to start with a visual inspection of the internals (likely involving several photos posted to the forum with the question of "does this look OK?" ). Andrew

1st Jun 2022, 9:20 pm	#3
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Tandberg TD20A-SE Repair and Restoration The above document seems to refer to valve kit with things like wax capacitors, not late 70s solid state gear that has likely seen use fairly recently. I have been working on 1970s Tandberg kit like this for decades and never had to take any special precautions. My usual procedure is to power it up as normal, for two or three minutes, using all my senses (hot/smoky smells, wisps of smoke, odd noises, etc). Anything suspicious, be prepared to yank the plug right away. Power off, look again, then power on again for longer. Unless this unit has Rifa caps as mains or switch suppressors (which some Tandberg kit of this era has) then you needn't do any 'preventive replacement', like many US forums have as some kind of golden rule among their less technical posters. Indeed, you'll likely just introduce other problems. You already have a loose spool table, you could look at sorting that out first. The you will be able to thread a junk tape and check for other problems. __________________ Regards, Ben. Last edited by ben; 1st Jun 2022 at 9:31 pm.

1st Jun 2022, 9:34 pm	#4
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,335	Re: Tandberg TD20A-SE Repair and Restoration You're quite right Ben, I should have qualified the somewhat zealous tone of the doc in capacitor replacement! I have had a lot of trouble with Frako and tantalum bead capacitors in late '70s gear, so I'm just cautious now.

1st Jun 2022, 11:30 pm	#5
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,672	Re: Tandberg TD20A-SE Repair and Restoration If it's been powered up recently anyway, I'd suck it and see. Rifas apart, I would expect anything spectacular.

2nd Jun 2022, 9:21 pm	#6
andrewferguson Hexode Join Date: Aug 2016 Location: Edinburgh, Scotland, UK. Posts: 262	Re: Tandberg TD20A-SE Repair and Restoration Thanks all for your help so far. I powered on the machine today and there were no pops or bangs. After some testing (none of it involving a reel of tape yet), I have now confirmed a number of issues: The capstan does not spin. The pinch roller arm is very slow to move when play is engaged. The three left-hand-side buttons (power, speed and reel size) are broken, requiring them be held in to work. The left reel table is broken (snapped plastic) and the right is cracking. The service manual is fantastic in detailing how to take apart and service these machines (really a step-by-step "for dummies" guide) and I have been following closely so far. Oh, and the little cartoon drawings contained within are fun too! I have taken the front top cover off, and it was immediately obvious why the capstan wasn't spinning - the belt had broken. Additionally, the belt for the tape counter is very loose, so could do with replacing. Looking on ebay, there are a few sellers that sell a "belt kit" for this machine, but the cost is quite prohibitive (not helped by all these sellers being US-based) - the total cost including postage comes to over £30. A much cheaper solution would be to get a generic belt that would fit. I've measured my belt and it is 345mm long and 5mm wide. This gives a diameter of 110mm, but I suspect by belt has stretched a bit with age, so if I ordered one I'd need to reduce the diameter a bit. I don't suppose anyone here knows the dimensions of the original capstan belt this machine needs? (Sadly the service manual does not say.) Ditto for the tape counter belt (a square one that I haven't looked at yet, since it will require a bit more patience to remove). Many thanks again for the help so far!

2nd Jun 2022, 9:37 pm	#7
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Tandberg TD20A-SE Repair and Restoration Look at this video just before the 1min mark. The pinch is activated by a worm gear, there will likely be hardened grease there. Do not keep using it till this is cleaned off as it may place undue stress on the gear teeth. __________________ Regards, Ben.

2nd Jun 2022, 9:38 pm	#8
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Tandberg TD20A-SE Repair and Restoration A number of sellers on the German ebay site list a belt set for the TD20A ('belt' in German is 'Riemen'), although the cost is about the same, being EUR 20,- for the belts and EUR 10,- for postage (at least to Sweden, might be different to the UK I guess). Not having any experience with this particular model, I would think a generic belt would work. Normally one would figure the length of an unstretched belt (i.e. measured with a piece of string for instance) minus 5 to 10 per cent.

4th Jun 2022, 3:54 pm	#9
andrewferguson Hexode Join Date: Aug 2016 Location: Edinburgh, Scotland, UK. Posts: 262	Re: Tandberg TD20A-SE Repair and Restoration I've found an ebay seller that has 5mm belts of varying sizes. My (snapped) belt has a diameter of 110mm, the available sizes are 110mm, 106mm, 103mm, 100mm, 97mm, 94mm and 88mm (and smaller sizes but I suspect anything below 88mm will be really too small). Not having much experience with estimating belt sizes (usually I order a kit for a particular machine, or have belts on hand I can try and see), has anyone got a rough idea of what belt I should pick? Right now I'm erring towards the 94mm one, but I don't want it to be too tight. I've also looked out what grease I have for re-greasing the worm gear. The type I have on hand is "Castrol LM" grease (see attached picture). Is this suitable or is there a particular type that members here would recommend? Attached Thumbnails

4th Jun 2022, 4:56 pm	#10
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Tandberg TD20A-SE Repair and Restoration You need lighter grease than that. I use CRC lithium-EP white grease which has served me well in general mechanical situations. In applications like this you only need a light smear. As for belts, I'd go for the 110mm. From what I've read this seems the size. Is yours the high speed ( top speed:15 ips) or low speed (7 1/2) version? __________________ Regards, Ben.