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 Stereo pickup cartridge to mono amplifier connection
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 Return to top of page · Post #: 1 · Written at 8:28:17 PM on 12 August 2017.
Gandhn's Gravatar
 Location: Windella, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 266

I have just replaced the cartridge in a Garrard 4 speed record changer, connected to my Scharnberg Strauss Tablegram, as the original crystal had turned to liquid.
I am pretty sure that it used to work with a 39K resistor in series with each channel output, the common going to the volume control.
With the new cartridge playing a mono record, there is a high level of surface noise and a faint audio signal. The output is fine from each channel, the other disconnected, but when combined, I get the faint signal and high surface noise.
I don't have a scope any more to check the phase of each channel, but I took a punt and thought the two channels were out of phase and cancelling out. I reversed the + and - connections on one side of the cartridge and it works as it should.
Does anyone have experience with this situation, as I am puzzled by it? Is it possible my new cartridge has + and - reversed on one channel, which my lead swap has corrected?
Harold


 
 Return to top of page · Post #: 2 · Written at 9:42:53 PM on 12 August 2017.
Vintage Pete's avatar
 Location: Cromer, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 564

Hello Harold,
I just restored the mechanics for a Garrard 121, Ive done a few turntables, I do the mechanics side of them. I Restored one for Ian and and its all working fine and Ian Robertson put the new type cartridge in it and he went through what was needed to do it,
So he is the guy that would have the answer you are looking for .I was a mechanic by trade years ago so the mechanics of turntables I understand and repair them for people sometimes
But as you know I know nothing about electronics .
So I did the mechanics for Ian and he did the cartridge change over .but it all works great and the owner has it back in the unit now..
Drop Ian a line,,
All the best Pete
L


 
 Return to top of page · Post #: 3 · Written at 9:54:45 PM on 12 August 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3972

Phase cancellation seems plausible,


 
 Return to top of page · Post #: 4 · Written at 10:39:56 PM on 12 August 2017.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 608

Yes definitely phase cancellation.

Sometimes the pinouts on cartridges can be misleading. What you did to fix it is exactly what I would have done!

There is also the possibility that the internal connections on your new cartridge were made incorrectly at the factory. If it is a NOS cartridge, it might well have been a set-maker's factory reject!

Kriesler used to reject large numbers of 6GV8s in TVs due to vertical sync issues. Philips said they were within spec so Kriesler were left with a stack of 6GV8s and a problem. They solved it by creating the 11-99 mantle radio!


 
 Return to top of page · Post #: 5 · Written at 9:51:48 AM on 13 August 2017.
Gandhn's Gravatar
 Location: Windella, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 266

Many thanks for your feedback, it makes perfect sense now.
When you think about a stereo cartridge playing a mono record, if the needle moves left in the track, then I can see that one channel will produce a positive voltage and the other will produce a negative voltage. By reversing one channel now both are in phase.
Problem solved!
Harold


 
 Return to top of page · Post #: 6 · Written at 4:03:01 PM on 22 August 2017.
Gandhn's Gravatar
 Location: Windella, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 266

Now that I have this project working, I would like to share its history, as it is a bit special and the only radio I kept back from my sale last year.
I received a phone call from a lady in Melbourne saying she had a Scharnberg Strauss radiogram looking for a new home. She had googled the name, Scharnberg Strauss and my name appeared because I had listed 4 SS mantel radios on Radiomuseum. She only had my name, no phone or address, but she looked in the phone book for a Harold Norrie and I was the first one she called.
Having no room for a big radiogram and not knowing the model, I initially had little interest, but as she described it, I felt it was pretty unusual and started my research on this radio. I am pretty conversant with the manufacturer and soon found some advertising in Adelaide newspapers, via TROVE. I called back and said I would love to have it, the problem being how to get it from Melbourne to Maitland. She couldn't pack it securely and Pack and Send quoted a couple of hundred dollars.
It transpired that she was travelling to Canberra in a couple of weeks and a fellow Canberra HRSA member was coming to Sydney for a meeting the following week. As luck would have it, they were in adjoining suburbs and a handover was set up. I attended the meeting to collect it and complete its journey.
I had the cabinet refinished and I did the electrics, including the record changer, with an old cartridge replacing the original. The replacement also failed due to moisture, ( a crystal type) and I replaced it with a ceramic cartridge, the subject of my earlier post.
The part of the restoration that sets it apart are the two clear panels behind the knobs. I did the artwork with Open Office Draw and asked Michael Raanan to print them, as he has a special printer that can print a solid colour, gold in this case.
Harold

Scharnberg Strauss Tablegram
Scharnberg Strauss Tablegram


 
 Return to top of page · Post #: 7 · Written at 7:17:28 PM on 22 August 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 4375

Photos uploaded to Post 6. I included a close-up of the control knob detail.

A very good restoration here. In 28 years of collecting I've never seen a tablegram by Scharnberg Strauss.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
Brad.

A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 8 · Written at 10:30:23 PM on 22 August 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3972

Nice story, and a very tidy resto.

Technical information on Scharnberg Strauss gear has usually been hard to find. The company doesn't seem to have be willing to contribute data to AORSM.


 
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