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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 12th Feb 2021, 1:09 am   #1
Katar83
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Default Grundig TK5 Resto

Hi there,

New to tapes and got a free TK5 locally, all good and working beautifully now after replacing ~15 capacitors (most WIMA and only a single one still within spec), sorting out capstan and a number of mechanical issues.

Few pics and videos here:

https://photos.google.com/share/AF1Q...FUWGs3Q1FGdnl3

It's a homemade recording by the way from 1956, made in Glasgow, possibly of unknown singer/actress, maybe someone will know who she might be?

Anyway, last thing I wanted to do is to replace 2 foam pads in the lid that used to hold the tapes when it was closed but have no idea of the size and original pads disintegrated probably 50 years ago and only two old glue stains are left where the pads were.

Does anyone knows or might have a similar Grundig recorder with these still intact and could share the width and height of these foam pads and maybe what material are they?
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Old 12th Feb 2021, 10:27 am   #2
vinrads
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Default Re: Grundig TK5 Resto

Hi, very nice, the pictures take me back to when I used to repair these they always worked well after the capacitors had been replaced. I had almost forgotten about the squirrel cage motor, thanks for the pictures. Mick.
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Old 12th Feb 2021, 11:14 am   #3
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Default Re: Grundig TK5 Resto

The photo of the inside has given me a preview of what I am going to find when I open up the one I pulled out of a waste paper bin a couple of years ago.
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Old 12th Feb 2021, 11:25 am   #4
Ted Kendall
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Default Re: Grundig TK5 Resto

The original pads were circular, of yellow/brown open cell foam rubber, about 2" diameter and 1" thick. Lasted well for about twenty years...
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Old 12th Feb 2021, 11:48 am   #5
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Default Re: Grundig TK5 Resto

Most of the foam pads on my various old Grundigs are missing or turned to dust including my TK 5.

Absolute size is not critical as long as the depth is sufficient to make good contact with the spools so that the spools do not come loose during unit being moved. Photo of my TK 27 pads are 50mm diameter and around 18mm high/deep. Foam/sponge is quite soft with some firmness.

David
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Old 12th Feb 2021, 1:18 pm   #6
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Default Re: Grundig TK5 Resto

I made a couple from grey foam pipe lagging for a Philips machine.
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Old 12th Feb 2021, 1:53 pm   #7
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Default Re: Grundig TK5 Resto

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Originally Posted by IvorBlister View Post
I made a couple from grey foam pipe lagging for a Philips machine.
That’s a good idea, I’ve always wondered where to find replacements since foam rubber seems to be difficult to cut neatly and not so easy to find locally. There used to be a stall in Coventry market that sold all shapes and sizes.

Anybody else found a useable replacement?

Oddly enough every single original one from every manufacturer I’ve seem has always disintegrated in time..... except one! Elizabethan ones seem to last forever.

Peter
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Old 12th Feb 2021, 5:33 pm   #8
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Default Re: Grundig TK5 Resto

Quote:
Originally Posted by Refugee View Post
The photo of the inside has given me a preview of what I am going to find when I open up the one I pulled out of a waste paper bin a couple of years ago.
I'm going to make this much easier for you so you can't drag it forever now

0.01uF - 125V
0.05uF - 500V
0.05uF - 250V
0.02uF - 125V
0.022uF - 500V
0.1uF - 500V
5000pF/5nf - 125V
0.05uF - 125V
0.25uF - 90V
0.01uF - 500V
1000pF/1nF - 1000V
5000pF/5nF - 250V
0.25uF - 500V

All apart from the last one were shot and I paid £3 for replacement plus £4 post.

Obviously these are no longer available and all current values can be found on this great forum here:

https://www.vintage-radio.net/forum/...ad.php?t=88767

You might also need a start capacitor as per attached pic, I've used 1.5uF 450V and a couple of electrolytic caps that were fine on mine, think one was 40uF and ~400V and other was a bit smaller. Might still replace them later. Start cap was ~£3

Many thanks to all re foam pads, I've stolen these 'make up blenders' from the missus , they have perfect diameter(55mm) but are not as tall(only 10mm) so I might have to stack two of them up, hopefully super glue can hold them together. They are super cheap though apparently and widely available.

Couldn't find anything more suitable so far so if anyone know of a better ready solution please let us know.
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Old 13th Feb 2021, 1:06 am   #9
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Default Re: Grundig TK5 Resto

I am pretty sure I have got all those capacitors in yellow 630V axial form.
Those face paint pads will work fine if you really do want to carry the recorder around with a tape threaded or reels stored on the hubs.
I have not yet set a time to do my two Grundigs. The bin find was a TK5 with one button missing and the hinges so rusty that the screws pulled out when I opened the lid. It doesn't look like it has been damp enough to make the lid delaminate.
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Old 13th Feb 2021, 10:33 am   #10
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Default Re: Grundig TK5 Resto

Hi
It would also be a good idea to clean the Rec/Play relay contacts as they can cause motor boating at hi volume levels (common impedance coupling).
I use a piece of stiff cardboard soaked in IPA and then the same thing with a very thin smear of silicone grease. I only use RS Components grease as it does not appear to migrate like some other types.

John
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Old 13th Feb 2021, 11:14 am   #11
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Default Re: Grundig TK5 Resto

For foam pads, I have found that garden “kneelers” are a good source. You can usually slice a bit off without ruining them and they are frequently offered in Lidl, Poundland etc.
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Old 13th Feb 2021, 11:17 am   #12
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Default Re: Grundig TK5 Resto

Pipe lagging is a brilliant idea!

How about a slice of one of those “ water woggle” things used to teach swimming? I think they are sometimes called pool noodles too. Not sure about the colours though!

Re. the garden kneelers, one could try a hole cutter of appropriate size at a slow speed.
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Old 13th Feb 2021, 12:23 pm   #13
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Default Re: Grundig TK5 Resto

In my second job as a teenager, I was sometimes given the job of a blanket change of all those treacle lookin wima caps. Quite a few split.
Mullard mustards were our replacements.
That was 50 years ago!
Rob
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Old 14th Feb 2021, 7:33 pm   #14
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Default Re: Grundig TK5 Resto

Quote:
Originally Posted by John Caswell View Post
Hi
It would also be a good idea to clean the Rec/Play relay contacts as they can cause motor boating at hi volume levels (common impedance coupling).
I use a piece of stiff cardboard soaked in IPA and then the same thing with a very thin smear of silicone grease. I only use RS Components grease as it does not appear to migrate like some other types.

John
Thanks I haven't thought about that, will have a look at the contacts there. Got plenty of IPA and various other chemicals used in electronic repairs I've used to do in the past.

Generally I'm very happy with how it works and sounds, I'm well surprised at the sound quality too and the whole thing is incredibly loud at full volume(and I have a 1000W worth of speakers and woofers here to compare to)

Re foam pads, generally there are plenty of materials that could be used here but ideally I want something precut at least on 2 surfaces so it looks factory, cutting pads completely from scratch will pretty make these squares instead of circles

I've also ordered a GCM3 microphone for it now and a couple of spare tapes so looking forward to playing more with it. I'm not sure how that tape even lasted that many years. My father has a few from the early 70s and they slowly disintegrating now when this tape presumably much older seems perfectly fine.
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Old 14th Feb 2021, 8:22 pm   #15
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Default Re: Grundig TK5 Resto

As you probably know the GCM3 is a condenser microphone and requires a nominal 100V DC polarising supply that the TK 5 provides. On my TK 5 the polarising supply was 0V due to shorted capacitors, you have probably changed the relevant caps but just for reference here is Thread link where Post 1 covers the polarising supply.

David

https://www.vintage-radio.net/forum/...d.php?t=163463
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Old 14th Feb 2021, 8:54 pm   #16
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Default Re: Grundig TK5 Resto

Quote:
Originally Posted by Katar83 View Post
I'm not sure how that tape even lasted that many years. My father has a few from the early 70s and they slowly disintegrating now when this tape presumably much older seems perfectly fine.
As a rule, polyester based tapes from the 1950s and 60s last pretty well, although acetate based types are nearly all brittle by now, and are prone to shedding lumps of oxide. Around 1970, synthetic binders came into use, and many brands using these suffer from "sticky shed" as the binder deteriorates. Baking makes the tape behave for a while, certainly long enough to get the signal off. I think the palm goes to BASF for longevity - it seldom, if ever, gives trouble, apart from a few batches in the 1990s - and Emitape runs it a close second.
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Old 14th Feb 2021, 10:11 pm   #17
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Default Re: Grundig TK5 Resto

A sharpened piece of tube of the the right diameter makes a convincing foam cutter. Coincidentally enough in a small world sort of way, we had an upholstery supplies stall in Coventry Market 40yrs ago
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Old 15th Feb 2021, 12:23 am   #18
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Default Re: Grundig TK5 Resto

Quote:
Originally Posted by DMcMahon View Post
As you probably know the GCM3 is a condenser microphone and requires a nominal 100V DC polarising supply that the TK 5 provides. On my TK 5 the polarising supply was 0V due to shorted capacitors, you have probably changed the relevant caps but just for reference here is Thread link where Post 1 covers the polarising supply.

David

https://www.vintage-radio.net/forum/...d.php?t=163463
Yes I saw your resto thread before signing up here, very helpful. One thing I was going to ask, what's the voltage on the smaller capacitor, I know one is 40uF/385V and the smaller is 100uF(?) but not sure on voltage? If you still have original capacitors let us know, will save me a bit of work.
I have to admit, I don't have a leakage tester so may as well swap these at some point, capacitance wise, they are bang on where they should be though.

Also, for the sake of serial numbers, mine is a bit earlier than yours

Great to know re tapes, I think there is one BASF tape for sale at the moment so I'll probably get that tomorrow, I'm hoping I can record myself for the future old me so would be great if the tape lasted another 40 years or so
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Old 15th Feb 2021, 2:37 pm   #19
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Default Re: Grundig TK5 Resto

Ok, found schematics now which says, 200uf 30V and 40uf 350V, didn't you use 100uF on yours David or am I missing something here?

Also, one more question. Any reason to replace two core wire with a grounded one? This one is still ok, just painted over in few places and obviously has a wrong plug so could swap it eventually too.

I've received beautifully looking Grundig GCM3 microphone this morning too and can report that it works great and recorded sound quality is surprisingly good, I'd say better than my Sony tape recorder I've been using 25 years ago
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Old 15th Feb 2021, 5:19 pm   #20
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Default Re: Grundig TK5 Resto

Pretty sure I threw those capacitors away, am sure it (C36) was 100uF, 4 different schematics show it as 100uF/70V, strange if your schematic shows 200uF/30V

30V also would be rather close to the actual voltage of around 27V, I went over the top with my 100uF at 450V because it was just what I had to hand and works fine.

Where practical I nearly always replace 2 core mains cables with 3 core so as to have an earthed chassis. Also sometimes the 2 core cables are poor condition so need replacing anyway. Most of the cables either have 2 pin plugs or poor condition 3 pin so always replace the plugs with a new 3 pin. None of this is absolutely essential but I feel happier from a safety point of view.

Yes the GCM3 are really nice looking.

David
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