Hello!(Refurbishing Recordio, ISO Astatic m41)

[Kat]

I currently don’t have the test equipment to provide high voltage tones but as soon as I figure out where I can do that, I’ll try it.

Little update, I found out I had the stylus on backwards so I did a few more tests with it in the right spot on plastic plates and still... nothing. The grooves are all straight and something seems to be canceling the sound out. I feel like I should at least be getting some recording.

[markrob]

No Special equipment is required. All you have to do is feed a 1Khz sine wave test signal into the line input of the Recordio and measure the output voltage that appears at the two terminals of the cutter head with any AC voltmeter (analog or digital). You should be able to generate a 1khz sine wave using any DAW program (e.g. Audacity) and play that back from a computer into the input of the Recordio. Use the record level meter on the Recordio to set the level.

[Kat]

Maybe I should try a direct setup haha, but I created a 1khz tone with audacity, moved the file to my iPad, and connected it to the recordio. I can only get about 30 volts AC from the amp to the cutter head. Would running it directly from the computer make any difference?

So I’m assuming I have a bad amp, at least in the microphone section of the circuit. My local radio museum (The Pavek Museum) offers a vintage radio service workshop, and probably oscilliscopes, so I’m just going to wait for that.

[markrob]

Hi,

30 Volts is pretty low, but are you sure you are driving the input with enough signal to get the amp to output full power? If you gain access to a scope, you will be able to see if the 30 Volts is a clean sine waveform or is clipping or otherwise distorted. Is there any level indicator on the Recordio that might tell you if you are getting a good signal level? Even with only 30 volts, you should be able to get some sound recorded. Were you reading the 30 Volt signal with the head connected. If not, see if connecting the head loads down the amp and reduces or kills the signal.

Mark

[ymg200]

If you install a stylus and couple it the bottom of a solo cup, it will act as a speaker. You can feed audio to the head via your amp and you should get a pretty loud acoustic output. It will be tinny and without any bass, but if if its loud, you are probably in good shape to cut with it.

Mark,
I am following this thread to figure out how to test 6A10 Recordio that I considering getting. I'm new to cutting lathes and have zero experience so far, not considering my online research. I'm looking at this machine and trying to understand what it takes to bring it to life, if possible at all.
Could you explain the sound test that you have mentioned above? I don't understand what "couple it the bottom of a solo cup" means.
Thank you.

[markrob]

Just make contact with the bottom of the solo cup and the tip of the stylus or 1/16" drill bit. The cup becomes a speaker cone and is vibrated by the stylus.

[ymg200]

Oh, I didn't realize that you were talking about the plastic cup Having a cup to sound makes a lot of sense to me as I collect old mechanical phonographs.

What size is a "line in" jack in Recordio? Is it 3.5mm? Can I use a mono 3.5mm cable to feed the signal?

[Kat]

Hi,

30 Volts is pretty low, but are you sure you are driving the input with enough signal to get the amp to output full power? If you gain access to a scope, you will be able to see if the 30 Volts is a clean sine waveform or is clipping or otherwise distorted. Is there any level indicator on the Recordio that might tell you if you are getting a good signal level? Even with only 30 volts, you should be able to get some sound recorded. Were you reading the 30 Volt signal with the head connected. If not, see if connecting the head loads down the amp and reduces or kills the signal.

Mark

The head was connected at the time when I measured the 30 volts off the iPad. It’s a salvaged console recordio so as far as I know, there’s no built in audio indicator.

I just ordered a full schematic’s worth of resistors and I’m going to start working on getting the amp a bit louder.

I’m guessing turntable wobble could be a problem and there’s also something wrong with how the head is attached in that somehow the head/needle are bouncing and losing the sound. I’d like some help on where these pieces actually go since I’m suspecting I put them in wrong.

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[Kat]

Oh, I didn't realize that you were talking about the plastic cup Having a cup to sound makes a lot of sense to me as I collect old mechanical phonographs.

What size is a "line in" jack in Recordio? Is it 3.5mm? Can I use a mono 3.5mm cable to feed the signal?

It should be just a standard RCA jack. Thanks for following this, that’s my goal, to try and demystify recordio restoration for anyone interested. I’d be happy to answer any questions.

My first suggestion for restoring your Recordio if you haven’t already is to buy a schematic and some replacement electrolytic capacitors.

[ymg200]

I went to inspect the machine today, but I couldn't test it because the audio cable that I had with me had the 3.5mm plug, but it turned out that Recordio has a 1/4" jack.
Testing with the mic didn't succeed either because the mic cable broke off its connector.
Touching the mic connector with bare mic cable or with the 3.5mm plug of my audio cable did produce some screeching from the recording head.
What is interesting, at some point Recordio has picked up some radio station and the sound was loud and clear. This machine has no radio, it is just like the one pictured here: https://www.radiomuseum.org/r/wilcox_gay_6a10.html I am not sure how it could pickup a radio signal and whether it is a good or a bad sign that it did. I suppose that some element in the circuit has lost its shielding and turned into an antenna. I don't have the schematics, so I'm blind.
I'll give it another try once I get the audio cable with a 1/4" plug.

Let's say the cutting head is not completely dead (I did hear some screeching from it after all). Can I replace the crystal myself? I've seen posts here about growing a Rochelle salt crystal. Is it feasible to replace the crystal in the head without a special equipment? I am surprised that I haven't seen instructions how to do so in this form or anywhere else.

[Kat]

Let's say the cutting head is not completely dead (I did hear some screeching from it after all). Can I replace the crystal myself? I've seen posts here about growing a Rochelle salt crystal. Is it feasible to replace the crystal in the head without a special equipment? I am surprised that I haven't seen instructions how to do so in this form or anywhere else.

No clue how you got a radio signal but my guess would be that all the circuitry would still be there to amplify a signal if there was one.

Unfortunately the crystal repair process is really bottlenecked. Until others come forward with their findings, the only expert really is Gib of Westech. Does the cutting head have a screw and can you use a paper clip or drill bit as a needle to see if the head can move it? I got sound too but wasnt able to get any needle vibration until I had the head rebuilt. The crystal can weaken and crack so just hearing sound isn’t enough.

[ymg200]

I'm thinking that maybe the mic served as an antenna....
I will go see the machine again and this time I'll bring the 1/4" audio cable. The head has the original needle attached, but I didn't feel any motion when I touched the needle. I expect that feeding an audio to this machine will tell me more about it's condition.

[Kat]

I'm thinking that maybe the mic served as an antenna....
I will go see the machine again and this time I'll bring the 1/4" audio cable. The head has the original needle attached, but I didn't feel any motion when I touched the needle. I expect that feeding an audio to this machine will tell me more about it's condition.

Ok! Let us know what happens.

Meanwhile my full complement of resistors has arrived. I’m starting with the high wattage ones and am already getting results. The AM is LOUD now. Definitely enough to fill an entire 1940s living room if I had the right speaker.

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However, the signal to the cutting head is yet to be improved and I am still getting silent grooves.

[ymg200]

Kat,
You've got a nice and loud sound out of your machine. It sounds like it has a lot of potential to record. What voltage do you get at the head at 1KHz input?
I finally got my machine, but didn't have a chance to test it thoroughly. The only test that I did when buying it was recording on a plastic plate, which didn't give encouraging results. The groove came out with no sound in it. I'm swamped with work and have a couple of house projects that I need to finish before I can start tweaking the Recordio, so it will be some time before I can report any progress. Mine is 6A10 model, it doesn't have a built in radio.

[Kat]

Kat,
You've got a nice and loud sound out of your machine. It sounds like it has a lot of potential to record. What voltage do you get at the head at 1KHz input?
I finally got my machine, but didn't have a chance to test it thoroughly. The only test that I did when buying it was recording on a plastic plate, which didn't give encouraging results. The groove came out with no sound in it. I'm swamped with work and have a couple of house projects that I need to finish before I can start tweaking the Recordio, so it will be some time before I can report any progress. Mine is 6A10 model, it doesn't have a built in radio.

Yeah, I hope. What you’re listening to is the speaker rather than the cutting head. For some reason the sound isn’t effectively making it all the way to the cutting head.

For your recordio, you definitely need to send the cutting head in to WestTech for a rebuild.

[ymg200]

What voltage do you get at the cutting head when you send 1kHz signal?

[Kat]

What voltage do you get at the cutting head when you send 1kHz signal?

It was only about 30 volts, nowhere near the necessary 180 or whatever.

[Kat]

I may have found a possible solution. There is a large 2 watt resistor that according to the photofact sheet is the “decoupler”. It is linked to about five different things including the cutting head transformer, and is reading 15k instead of the 10k ohms it should be. I’m planning on replacing that. -Kat

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[Kat]

So the resistor appears to have a minimum effect. Radio repair folks say to never replace the micas and ceramics but I ordered some just to be safe. I’m getting an unexplained sudden voltage drop in the cutter. It’s loud-ish for about ten seconds and then fades which seems more like a capacitor issue than a resistor issue.

[Kat]

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Major update!

I have just finished attending a repair class and replaced the remaining tubes, including the eye tube which is how the recording level is determined in the first place. Replacing the “limiter” and the cutter amp tube seems to have helped the most as the needle movement is a lot more consistent, including a response to the microphone. It was probably the limiter because the tube was almost dead. So electric issues are all but fixed.

However the turntable still needs a thorough cleaning. It spins at exactly 78, but I’m getting silent untrackable grooves that seem to have a hill and dale quality to them.

Kat

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