UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players

Notices

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

Reply
 
Thread Tools
Old 6th May 2023, 4:30 pm   #1
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Grundig TK820/3D

Just bought this Grundig, it's in very good condition for a 67 year old. It appears to be completely original, so I'm looking for advice on what to check and what to replace. I know the Wima "black toffee" capacitors are all going to need replacement, but what do you tape recorder experts know about common problems on these machines? Is it considered necessary to replace the metal rectifier with silicon diodes? Any advice would be appreciated. I used to repair the more basic models from Grundig, Philips etc back in the early 60's, so have a working knowledge of tape recorders. Sorry if I have rambled or sound disjointed, but SWMBO is watching the King's do on TV.
Breton56 is offline   Reply With Quote
Old 6th May 2023, 4:35 pm   #2
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Grundig TK820/3D

It's not essential to replace the metal rectifier, but I would normally do it if doing any other work or if the HT is low. They do deteriorate sooner or later.
paulsherwin is online now   Reply With Quote
Old 6th May 2023, 5:09 pm   #3
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Re: Grundig TK820/3D

Thanks for the speedy reply. Maybe the recorder had very little use as head and guide wear is minimal. I have not started any work on it yet but as I'm approaching 80 I work very slowly and hopefully methodically.
Breton56 is offline   Reply With Quote
Old 6th May 2023, 11:04 pm   #4
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
Default Re: Grundig TK820/3D

The 25V supply rectifier is an AEG component under the chassis near the front. It's unreliable and will blow the 500mA fuse and disable the machine. The HT rectifier is a Siemens bridge mounted on one of the chassis uprights. It is reliable. Both are selenium.

Replace the Wima "toffee" capacitors and keep an eye on the relay contact snubbers which are 0.2uF + 100 Ohms. Ensure the one way clutches inside the intermediate pulleys are free as the tape wound springs within them are irreplaceable now. Check the rubber rings under the spool top hubs which go tacky. These ensure the reel clutches lock when the hub magnets are energised on fast wind.

Nice machines. Tape guidance is sometimes a problem when changing tape travel direction with the track buttons.

Leon.
Leon Crampin is offline   Reply With Quote
Old 7th May 2023, 11:52 am   #5
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Re: Grundig TK820/3D

Thanks for that Leon. My experience of Grundig recorders was mainly in the 60's and then mainly the more basic models. The hHT rectifiers were reliable then but I will take your advice re the LT. I haven't started any work yet, the seller said that everything works but of course I will proceed with caution.
Breton56 is offline   Reply With Quote
Old 7th May 2023, 2:05 pm   #6
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Grundig TK820/3D

Two out of the three 0.2uF +100 Ohm motor supply relay contact snubbers had badly leaked black horrible tar like gunge on my TK 819 as documented in this linked Thread :-

https://www.vintage-radio.net/forum/...d.php?t=162904

David
DMcMahon is offline   Reply With Quote
Old 12th May 2023, 1:09 pm   #7
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Re: Grundig TK820/3D

Thanks for all replies, will do a mechanical inspection first, order some caps and go from there. More some time later.
Breton56 is offline   Reply With Quote
Old 27th Feb 2024, 2:22 pm   #8
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Grundig TK 820/3D

I'm now ordering spares following advice from Leon. Can't find a small bridge listed at Cricklewood for the 25volt supply and would it be wise to add series resistance to match the losses of the selenium rectifier? One of the snubbers has leaked pitch, so I would like replace all four, restuffing with new R and C but what ratings? There are two caps of 5000pF rated 250VAC in series across the mains supply with centre point connected to chassis, this value is well below any X type listed, so what to fit if no grounded inputs or outputs are connected the chassis is floating as mains connector has no earth wire (I may change this later). The rubber rings Leon referred to under the spools have disappeared with only a stain to show that there was anything there, so what can I use to replace these? All replies gratefully received.

Last edited by Station X; 27th Feb 2024 at 2:36 pm. Reason: Threads merged. Added a few spaces.
Breton56 is offline   Reply With Quote
Old 27th Feb 2024, 3:21 pm   #9
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Grundig TK820/3D

Is it important to you to restuff the original snubbers ? extra messy work for items that are not normally seen, easier just to replace the complete snubbers with new RC snubbers.

I have not checked the schematic but assume your snubbers will be very similar if not the same as the ones in my TK 819, as covered in linked Thread at Post 6.

David
DMcMahon is offline   Reply With Quote
Old 27th Feb 2024, 3:36 pm   #10
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: Grundig TK820/3D

Since these capacitors go from the mains to the chassis, failure (short-circuit) could cause a shock hazard. Therefore I would have thought they should be class Y (Y2)

5000pF = 5nF. I'd fit 4n7 class Y2 capactors which are not hard to obtain.
TonyDuell is online now   Reply With Quote
Old 27th Feb 2024, 6:37 pm   #11
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Grundig TK820/3D

Checking the TK 820/3D documentation the 4 potted snubbers are the same as the TK 819 namely 0.2uF + 100 Ohms.

If you wanted to restuff the original snubber cases using discrete components, ideally you should use X2 rated capacitors but you may find difficulty in finding suitable X2 capacitors that will fit inside the old cases.

David
DMcMahon is offline   Reply With Quote
Old 29th Feb 2024, 10:42 am   #12
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Re: Grundig TK820/3D

Thanks for all replies so far,,job on back burner again,more pressing problems,my wife has suffered a heart attack and stroke.Seems that finding material for the upper spool clutches might be the biggest challenge.
Breton56 is offline   Reply With Quote
Old 6th Mar 2024, 8:49 pm   #13
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Grundig TK820/3D

Really sorry to hear your wife's health problems, I hope she is OK.

Posts 13 and 14 of this linked Thread touched upon clutch material.

https://www.vintage-radio.net/forum/...d.php?t=123169

David
DMcMahon is offline   Reply With Quote
Old 6th Mar 2024, 11:31 pm   #14
Breton56
Triode
 
Join Date: Jul 2011
Location: Mumby,Lincolnshire
Posts: 45
Default Re: Grundig TK820/3D

Thanks David for your good wishes, also the link. Of course I have only my wife's health on my mind at the moment but I'm sure when I can get back to the repair, all will be achievable. Will take note of all advice and act on it when I get back to the repair.
Breton56 is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:22 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.