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Old 05-26-2016, 11:07 AM
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dtvmcdonald dtvmcdonald is offline
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help with dead 1938 cartridge

I have an RCA u-10 radio phono. I bought it to use as
the amplifier-speaker of the tt5 TV in the Repair forum. It works nicely as that.

Now I want to get the phono working. The turntable works OK but will have
horrendous rumble (which won't get to the speaker.)

The cartridge is of course dead. I thought that you could get them rebuilt ..
and you can. But the one that came with it is apparently an unrebuildable replacement.

Thus I need a new one. Do ones exist that will take the horrendous
force of the heavy tonearm? I suppose I could add a counterweight.
The amp has lots of gain, 0.4 volts is plenty.

Similar heavy arms were used in all the RCA U-xxx phonos of the day.
What do people do? I really want this to work. It would of course
never be really used any.

Sorry if this has been answered ... but searches failed. This is also posted on the radios forum.
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Old 05-26-2016, 11:20 AM
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maxhifi maxhifi is offline
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Send an email to Gary at the voice of music audio enthusiasts, I would be really surprised if he can't help you out. http://www.thevoiceofmusic.com

If it's an idler drive may want to send the idler in for a rebuild at the same time. I use wheel bearing grease with a few drops of oil on the centre bearing, it seems to reduce rumble to a lower level than using oil or grease alone. Also, a very good cleaning of all old grease and oil with isopropyl alcohol, and new rubber motor mounts.

Last edited by maxhifi; 05-26-2016 at 11:48 AM.
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Old 05-26-2016, 01:33 PM
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dtvmcdonald dtvmcdonald is offline
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Its drive is from the motor spindle to an 8 inch or so rubber tire on
the platter underside. Thankfully the tire is essentially OK: the
spindle was buggered and out of contact with the tire so no dent.
The motor mounts are rather hardened.

I found instructions for trying to fix the cartridge with a Rat Shack piezo,
and will try that. Its cheap.
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Old 05-26-2016, 05:03 PM
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Quote:
Originally Posted by dtvmcdonald View Post
I found instructions for trying to fix the cartridge with a Rat Shack piezo,
and will try that. Its cheap.
I've never heard of that before. Mind posting a link to those instructions?
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Old 05-26-2016, 10:02 PM
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dtvmcdonald dtvmcdonald is offline
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I'll post the URL tomorrow.

I succeeded. However, I used hot glue rather than rubber and silicone.
It may not last, but we shall see or rather hear. The cost is like $3.

I have no records to play, 50 are in the mail from the 'bay, cheap.
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Old 05-27-2016, 08:51 AM
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dtvmcdonald dtvmcdonald is offline
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The rebuild instructions are at

http://www.fidnet.com/%7Eseanbart/Ca...build_rev1.pdf
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Old 05-27-2016, 09:51 AM
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This has the straight tonearm which is round and heavy at the cartridge end, isn't it? I have a 1939 model console like that. Fortunately my cartridge is good. Those early cartridges used Rochelle salt crystals which degrade over time due to conditions such as humidity.
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Old 05-27-2016, 11:23 AM
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dtvmcdonald dtvmcdonald is offline
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Yes, the tone arm is big and fat and round and heavy. It looks straight,
but its fat and round because the cartridge is mounted at the proper angle
inside. Its suspension was not working right but Super Glue fixed it.
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Old 05-27-2016, 01:49 PM
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dtvmcdonald dtvmcdonald is offline
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I bought a 1930s big band record and a 1947 Horowitz Pictures at an exposition album,
both well worn, to try.

They sound as expected, noisy but there is no obvious problem like
the cartridge interior works bottoming out. There is plenty of
output for the garden AA5 amplifier, but not enough for
anything with lots less gain. I declare success for the rebuild.

As I said, but will the hot glue last?
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Old 05-27-2016, 02:21 PM
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Quote:
Originally Posted by dtvmcdonald View Post
Thanks for the link! At $40 bucks a pop to send out for a commercial rebuild I have not felt like paying to fix the carts in my 78 rpm rigs, but at ~$4 a pop doing DIY cart rebuilds I think all my 78 RPM phonos are going to be working soon.
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Old 05-27-2016, 02:22 PM
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Rubber and silicone will most likely last a lot longer.
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