Hello!(Refurbishing Recordio, ISO Astatic m41)

[Kat]

Hello, you can call me Kat! I’m a geology student living near Minneapolis. Home cut records have been a bit of an obsession lately and I have found myself repairing a salvaged console Recordio as my latest pandemic project. I currently have the turntable and AM working so far. I am stalled though where a lot of newbies end up— waiting for WestTech to open up for crystal head repairs again!

I got a question, how would I go about finding an M41 cartridge instead to replace it?

In the meantime I’m getting one of those Gakken toy record makers all the way from Japan just to mess around with.

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[emorritt]

If you do change to an M41 head (magnetic, not crystal) make sure you get a matching transformer because the output of the WG amp for the cutting head is off the plates of the tubes = high voltage; 180VRMS or there about. That will cook an M41 in seconds.

[piaptk]

Hi Kat, i think i have both an m41 and the matching transformer available for sale. Dm me if you are interested. Mike

[Kat]

cool, sent you a dm.

[Kat]

If you do change to an M41 head (magnetic, not crystal) make sure you get a matching transformer because the output of the WG amp for the cutting head is off the plates of the tubes = high voltage; 180VRMS or there about. That will cook an M41 in seconds.

good to know, I’ve heard there’s some re-wiring involved.

[Kat]

Finally wired up my cutting head and I’m getting some sound? It’s very quiet though and I have to put my ear to it but it is clearly coming out of the cutting head. Not bad for 75 years.

I’m going to assume I still need to replace it.

[Kat]

okay thanks for changing the title!

[Kat]

Little update! I just got my x-26 cutter back from Gib and I am not getting any sound at all. It was recommended that I finish replacing the capacitors and then send it back if there's still issues.

I have only replaced the electrolytic capacitors in my Recordio and not the micas or ceramics, which I'll be ordering soon. I'm of course paranoid I broke my cutter head somehow so is there any way I can test it in the meantime?

[piaptk]

You can check the continuity on the head with a multimeter. If its' 500 ohms AC (which I believe the crystal heads are) it will read 76(ish) ohms DC.

[Kat]

You can check the continuity on the head with a multimeter. If its' 500 ohms AC (which I believe the crystal heads are) it will read 76(ish) ohms DC.

Well, according to the multimeter, it’s an open loop. I still can’t imagine I fried it since the recordio appears to be outputting 75-ish volts and I started it off very quietly and never once heard any noise, radio or otherwise.

Either I did fry it, it broke in transit or the horror stories about needing multiple rebuild attempts I heard from the local vintage radio repair guy are true.

[markrob]

Hi,

Crystal heads will not measure any DC resistance with a multimeter (perhaps megaohms due to leakage). The head may need to go back to Gib. Prior to sending it, feed a 1khz signal to the input of the Recordio, put it into record mode and measure the output where the head would be connected using your multimeter set to AC volts with a full scale above 100 Vac. You should be able to see something in the range of 75-180 Vac at the head at full drive. If you do, then your amp is probably ok.

One quick check of the head would be to connect it to your multimeter (while not connected to your Recordio) set for a low AC volts range (maybe 0-2V). Install a stylus or better yet, A 1/16" drill bit in place of the stylus. Tap the stylus/drill bit in the side ways direction (as it would vibrate when cutting) and watch your multimeter to see if you get some voltage spikes. If not, it may be dead.

Mark

[Kat]

Hi,

Crystal heads will not measure any DC resistance with a multimeter (perhaps megaohms due to leakage). The head may need to go back to Gib. Prior to sending it, feed a 1khz signal to the input of the Recordio, put it into record mode and measure the output where the head would be connected using your multimeter set to AC volts with a full scale above 100 Vac. You should be able to see something in the range of 75-180 Vac at the head at full drive. If you do, then your amp is probably ok.

One quick check of the head would be to connect it to your multimeter (while not connected to your Recordio) set for a low AC volts range (maybe 0-2V). Install a stylus or better yet, A 1/16" drill bit in place of the stylus. Tap the stylus/drill bit in the side ways direction (as it would vibrate when cutting) and watch your multimeter to see if you get some voltage spikes. If not, it may be dead.

Mark

Thanks Mark. I am definitely getting a small spike in voltage when I tap the stylus. It goes from a resting voltage of 0.01 VAC up to 0.4 VAC. Seems promising!

I’ll check the amp next, but going to assume it’s down to one or two bad resistors or smaller value caps.

[Kat]

X-26 head works! Getting some sound and movement from the needle. It still seems pretty quiet though, is it supposed to be like that?

Pretty sure my only problem was a loose capacitor that was only barely touching ground. Re-soldered it and now I can hear tapping from the cutting head when in the phono slot and it works when on the cutter output.

One thing I’m still not sure about is how much more I can improve the amp but that can wait for now. Onto the first test cut.

[markrob]

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.

[Kat]

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.

yep sound is ok! any faintness to the sound seems to depend on how much of an am antenna is on there. Currently I just have a single RCA jack that leads to nowhere

[Kat]

Ok! I did some testing with a plastic plate. The grooves look nice, but there’s no sound. I’m thinking this is definitely not loud enough. My little Gakken Ez Maker with its 1.5 something volts is louder than this haha.

I’d rather not invest in a modern amp. Do I need to replace the ceramic and mica caps? There’s also a few resistors that are a couple hundred percent higher than they should be.

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[markrob]

Hi,

Generally, mica and ceramic caps don't need to be replaced. They are very stable over time. Paper and electrolytic caps don't age well and should be replaced. Old carbon comp resistors do tend to drift in value over life, but most circuits cans handle that pretty well. However if they have drifted as far as you have indicated, they should be replaced. Note that it can be misleading to measure resistors in circuit as the value can be affected by other components connected to the resistor in question. But, the effect of this is to reduce the value of the reading. I can't think of a case where I've measured a higher value unless the resistor in question was defective. To be sure, you should clip or unsolder one lead of the suspect part and measure it out of the circuit to verify. You might find the resistor is open and you were reading the circuit resistance.

Seems odd that if you ran the Solo cup test and had decent loudness that there would be no sound in the grooves. Could you hear anything from the head while you were cutting?

Mark

[markrob]

Hi,

Generally, mica and ceramic caps don't need to be replaced. They are very stable over time. Paper and electrolytic caps don't age well and should be replaced. Old carbon comp resistors do tend to drift in value over life, but most circuits cans handle that pretty well. However if they have drifted as far as you have indicated, they should be replaced. Note that it can be misleading to measure resistors in circuit as the value can be affected by other components connected to the resistor in question. But, the effect of this is to reduce the value of the reading. I can't think of a case where I've measured a higher value unless the resistor in question was defective. To be sure, you should clip or unsolder one lead of the suspect part and measure it out of the circuit to verify. You might find the resistor is open and you were reading the circuit resistance.

Seems odd that if you ran the Solo cup test and had decent loudness that there would be no sound in the grooves. Could you hear anything from the head while you were cutting?

Mark

[Kat]

Alright, hopefully the resistors are the only problem. I’ve replaced a few already and it seems a little louder but not enough. Looks like it’s just going to be guess and check from here on out.

I’m convinced it’s still not loud enough actually and that the solo cup test was too quiet. I don’t hear anything from the crystal when it’s cutting, unlike some youtube vids I have seen where the crystal can still be heard throughout.

[markrob]

I would check to see if the amp can deliver a clean 1Khz 180 Vac rms to the head terminals. If so, then the head is the issue. If not, then the amp may need some help.

Mark