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

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)

Notices

Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

Reply
 
Thread Tools
Old 21st Jan 2020, 6:19 pm   #1
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Radiogram pickup

The pick-up head in the photo is the wrong type which somebody has cobbled together from another deck. I appears to be crystal but does not work very well - low/poor output
Does anybody know what the correct one looks like or better still sell me one! it doesn't have to be working as I should be able to mend it. It's a Garrard ac7 motor/deck on a 1936 Ekco RG79 Radiogram
Attached Thumbnails
Click image for larger version

Name:	20200121_161616.jpg
Views:	167
Size:	67.4 KB
ID:	197538  
pentoad is offline   Reply With Quote
Old 21st Jan 2020, 11:20 pm   #2
Silicon
Octode
 
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 1,097
Default Re: Radiogram pickup

Some of the pickups from this era were moving magnet types.

The rubber supporting the moving parts can become rigid.

I have read that new 'rubber' supports can be made using neutral cure silicone.
Silicon is offline   Reply With Quote
Old 23rd Jan 2020, 3:09 pm   #3
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

I might adapt this pick up if I cannot obtain the right one
Attached Thumbnails
Click image for larger version

Name:	20200121_161739.jpg
Views:	78
Size:	55.9 KB
ID:	197643  
pentoad is offline   Reply With Quote
Old 24th Jan 2020, 9:35 am   #4
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 5,804
Default Re: Radiogram pickup

Hi, it may be possible to add a small amplifier to boost the sound if you cannot get the correct pickup

Ed
Ed_Dinning is offline   Reply With Quote
Old 24th Jan 2020, 11:24 am   #5
PaulR
Nonode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 2,074
Default Re: Radiogram pickup

Could you somehow hide a modern cartridge within that pickup? I imagine that it was put in to improve the sound quality and record wear over the original "blunderbuss" head. Seeing that it is in place it might be worth experimenting with a replacement cartridge before reverting to the original pickup type.
__________________
Paul
PaulR is offline   Reply With Quote
Old 24th Jan 2020, 11:47 am   #6
Edward Huggins
Dekatron
 
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 5,270
Default Re: Radiogram pickup

I think that replacement crystal pick up is a Rothermel from 1947. It might be possible to fit a more modern crystal type (e.g. a BSR TC8M) with a 78 stylus. The issue might be how this matches to the EKCO's pick up circuirty input impedence, which was designed for a magnetic type.
__________________
Edward.
Edward Huggins is offline   Reply With Quote
Old 24th Jan 2020, 11:52 am   #7
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

I'm not sure if this the type pick up that should there
https://www.radiomuseum.org/r/garrard_rc70b_rc_70.html
The input from the gram socket uses the TV4 magic eye as input stage which is connected to the output valve. Still don't know if the original would be magnetic or crystal
pentoad is offline   Reply With Quote
Old 24th Jan 2020, 11:54 am   #8
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

Quote:
Originally Posted by PaulR View Post
Could you somehow hide a modern cartridge within that pickup? I imagine that it was put in to improve the sound quality and record wear over the original "blunderbuss" head. Seeing that it is in place it might be worth experimenting with a replacement cartridge before reverting to the original pickup type.
Would it stand the weight though?
Weighs in at 60grams at the tip
pentoad is offline   Reply With Quote
Old 24th Jan 2020, 1:51 pm   #9
PaulR
Nonode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 2,074
Default Re: Radiogram pickup

I did wonder about that and the rather harsh stop mechanism at the end of the record but I assumed that it was a lot lighter than that in its modified form. The answer, of course, is that it wouldn't.

I wonder whether the whole arm has been replaced. It does look like the one on the RC70B but the adjustable speed governor looks older, more like the one on my McMichael 365 on this video https://www.youtube.com/watch?v=iLP5f7BnTAw.

When I was looking for a McMichael 365 I did come across one that had a very similar set up to yours. I think the description was that it had a Connoisseur tone arm. It might have been a standard "improvement" in the early years after the war.

Does yours still activate the automatic stop mechanism at e end of the record?
__________________
Paul
PaulR is offline   Reply With Quote
Old 24th Jan 2020, 2:07 pm   #10
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

Yes it has - the arm is pushed towards the back to start it and it stops automatically at the end.
The deck and arm are original, the head shell has been sawn off a Rothermel arm and glued on the bayonet end of the original headshell. I have stabilised it with epoxy putty as temporary fix just for test purposes.
pentoad is offline   Reply With Quote
Old 24th Jan 2020, 2:26 pm   #11
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 13,065
Default Re: Radiogram pickup

Photos can be deceiving, but that arm looks a bit too short as well.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 24th Jan 2020, 3:46 pm   #12
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

The clip on magnetic PU works fine after a test with it clipped onto a wind up gramophone and plugged into the radiogram. Plenty of loud volume, sounds a tad harsh and lacking in bass, not sure whether it's supposed to sound like that maybe the rubbers need changing, however there are fine wire connections in there going to the coil - so I may leave it. I might make a bracket and adapt it to fit the arm until I find the correct headshell / PU.
pentoad is offline   Reply With Quote
Old 24th Jan 2020, 6:10 pm   #13
PaulR
Nonode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 2,074
Default Re: Radiogram pickup

That sounds like a good idea. I have found that those of HMV origin then the rubbers may be ok. Garrard ones tend to have gone solid
__________________
Paul
PaulR is offline   Reply With Quote
Old 25th Jan 2020, 1:30 am   #14
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,695
Default Re: Radiogram pickup

Quote:
Originally Posted by pentoad View Post
The clip on magnetic PU works fine after a test with it clipped onto a wind up gramophone and plugged into the radiogram. Plenty of loud volume, sounds a tad harsh and lacking in bass, not sure whether it's supposed to sound like that maybe the rubbers need changing, however there are fine wire connections in there going to the coil - so I may leave it. I might make a bracket and adapt it to fit the arm until I find the correct headshell / PU.
Harsh and lacking in bass could well be due to solidified rubber parts, but could also be due to an impedance mismatch, or a bit of both.

Those electric pickups for gramophones are a rare and collectible item, so I certainly wouldn't spoil it just for the sake of that old modified single play record deck. There must be loads of old scrap Garrard decks kicking around that you can remove complete arms with heads from. That type of arm is always going to be way too heavy for a crystal cartridge of the TC8 type, so not worth considering. Some of those 78 only Garrard decks did have a spring arrangement a bit like a clothes peg spring to try to compensate for some of the weight, so you could try a modification along those lines, although as has been mentioned, if it's too light then it won't be able to trip the autostop and may cause groove jumping near the end of records.

Some of those pickup heads needed a transformer for matching to the amplifier. With a different head to the original one you may have to build a pre-amp stage for matching. Some times it's just a case of altering component values in the input circuitry. Those old magnetic heads usually need to see something like 50k on the input, while crystal heads need to see around 2Meg. Sometimes you can get away with just changing the value of the volume control pot if the input goes straight to that.
Techman is offline   Reply With Quote
Old 25th Jan 2020, 1:55 pm   #15
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

Well I fitted the magnetic PU ( Goldring )
It seems to work ok but weighs in at a hefty 100grams - Is that normal for a 30's gramophone?
The impedance is 2.3k ohms
Attached Thumbnails
Click image for larger version

Name:	20200125_125323.jpg
Views:	41
Size:	41.0 KB
ID:	197730  
pentoad is offline   Reply With Quote
Old 25th Jan 2020, 2:01 pm   #16
PaulR
Nonode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 2,074
Default Re: Radiogram pickup

I have just weighed the McMichael and that is 120g so yours is a positive lightweight!!
__________________
Paul
PaulR is offline   Reply With Quote
Old 25th Jan 2020, 3:17 pm   #17
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,695
Default Re: Radiogram pickup

It's my personal opinion that all those electric magnetic pickups cause more damage to 78s than an acoustic windup gramophone sound box does. There's often not a lot of difference in weight and the horizontal compliance, in my opinion, is worse on the electric pickup than the sound box. On a sound box, you've got a long stylus bar that pivots and swings over its length, giving really good compliance when adjusted properly. Whereas, with the electric magnetic pickup, there's really only the swing of the needle itself in the very short armature arrangement that it fits in, and if the rubber isn't all it should be, then that makes it even worse.
Techman is offline   Reply With Quote
Old 26th Jan 2020, 12:36 pm   #18
pentoad
Tetrode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 52
Default Re: Radiogram pickup

I agree
The rubber on this PU is still soft-ish so I don't think it needs replacing yet. But the weight of the arm and PU is enormous.
pentoad is offline   Reply With Quote
Old 26th Jan 2020, 1:01 pm   #19
PaulR
Nonode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 2,074
Default Re: Radiogram pickup

It is odd. Sometimes the rubber is still soft and sometimes it seems to have morphed into bakelite. The EMI derivatives seem to be the best.

If you do change the top suspension there is a fine line between getting the maximum compliance whilst still controlling the movement of the armature and leaving it too loose and getting odd high frequency distortion
__________________
Paul
PaulR is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 2:52 am.


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 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.