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.

Closed Thread
 
Thread Tools
Old 24th Feb 2016, 12:33 am   #21
MeerKat
Hexode
 
MeerKat's Avatar
 
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 296
Default Re: Grundig TM 819a Tape Deck

Thank you Leon and Roy for your encouraging comments and suggestions.

More progress today, record now works after I cleaned the pins on the EF86 and I committed a bit of muppetry connecting my Music boy – I got the connections wrong. After correcting things I was pleasantly surprised at the quality of the recording given the age of the machine. As you say Leon I need to check round the EM71, recording with the fans just touching gives a bit of distortion but backing off the level stops that.

I have removed the warped spool and found I could get a 1.5 thou feeler under the sintered bush flange part way round. I tried to seat it back down with a bit of judicious force but no deal so I put it in a fan oven set at 80c for half an hour to see if that would help. When I removed it the bush fell out and inspection showed the flange had a fracture part way round where it joins the bush proper. A bit of gentle squeezing in the vice has closed the gap up. As a check I reassembled the spool and found the warping now gone, result! Tomorrow I will strip it and glue the bush back in with epoxy.

I will start sorting the tape path next, I will carefully measure heights etc with my digital vernier before I disturb anything. Turning the guides to get a decent surface to the tape won't change the height much but I need to make sure all and the heads are lined up. I will polish the heads as well, there is a small step on them, am I right in thinking the heads plug in? And can you remember which screws on the R/P heads release them?

I'm quite enjoying this project but 'she who must be obeyed' thinks I'm getting a bit obsessed! But I can't complain she puts up with a lot!

Andrew
MeerKat is offline  
Old 24th Feb 2016, 12:04 pm   #22
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
Default Re: Grundig TM 819a Tape Deck

All of the "running" tape guides are solids of rotation and can be re-positioned to present an unworn surface to the tape. The head platforms are fully adjustable with springs under the 3 screws, so resetting the head height to match is no problem either. Hopefully, the capstan (motor) shaft will be unworn - it usually is, although it may need polishing.

You might want to choose "half a turn up or down" for the guides by observing the tape clearance to the spool cheeks as the machine runs.

All the heads plug in and the two R/P heads have nicely made mumetal cans. As I recall, there are 4 long small screws on top of each can, two of which just secure the can. It's all pretty simple and easy to adjust. I think the 2 screws with the slightly larger heads secure the can - but this may be stretching my memory too far.

Be careful with your vernier not to magnetise the heads - I think the guides are non-ferrous.

Leon.
Leon Crampin is online now  
Old 9th Mar 2016, 12:23 am   #23
MeerKat
Hexode
 
MeerKat's Avatar
 
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 296
Default Re: Grundig TM 819a Tape Deck

Thanks for your tips Leon, progress continues, all the Wima 'toffees' and Frako caps have been replaced now and I have replaced the Se diode associated with the EM71 with a NOS OA91 that I had, the action of the EM71 is much crisper now, I will have to reset the associated preset to make sure the actual recording level is correct, I have access to a scope that will help with this. I have checked the 10uf cap on the ECC81 cathode and it reads 12uf and easily exceeds 30 mega-ohms, not bad for it's age!

All the heads have been re-profiled to remove tape wear, I accomplished this by removing each one and with a rocking motion on a 320 grade stone removed the wear. They were finished off with 1200 grade paper, the finish is not mirror though. Before use they were de-magged. I am satisfied as lifting off the associated roller during play causes no noticeable drop off in HF (it did previous to re-profiling), well not to my ageing ears anyway!

The tape guides which were well out of alignment have been turned to present an unworn surface to the tape and as best I can, lined up ensuring tape comes off/on the reels without kissing the cheeks. I have carefully restored the pinch wheel surface, I mounted it in a drill turning at low speed and with 320 paper took the shiny surface off and again finished with 1200 paper, a steel rule was used to keep the paper flat. The solenoid was adjusted to compensate for the thou or so rubber removed. Tape transport is improved but not perfect, going one way there is still a slight 'curve' to the tape at he top of one guide. I have tried flexing various bits but can't eliminate it, annoying! I need a 2 track test tape or a decent recording from a known well aligned machine to set up the heads, I don't have either – any ideas?

Andrew
MeerKat is offline  
Old 9th Mar 2016, 2:15 pm   #24
ricard
Octode
 
ricard's Avatar
 
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,631
Default Re: Grundig TM 819a Tape Deck

I've polished heads by applying some polishing agent like Autosol to a piece of cloth, laid it on a piece of glass or other hard, flat surface, and polishing the heads just as you have done with the stone and paper. Brings the surface up to a mirror shine after the actual relapping. Just be sure to clean them off thoroughly afterward.
ricard is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:44 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.