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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 14th Sep 2020, 1:48 pm   #1
MeanDumpsterCat
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Default Ferrograph Series 5 Triggering RCD

Hello,

I finally managed to source a power cable for my Ferrograph. The first time I tried it, I connected it up to my variac and slowly introduced the current and it seemed to power up okay. (meter glows) however there was a loud 50hz vibration coming from the machine.

After that I connected it to the regular power outlet. The motor twitched a little but and then the power cut off entirely and I found out it had triggered the house breaker.

I'm going to take a look at it later (its stored somewhere quite akward at the moment) but are there any pointers as to where I should start looking for shorts?

Cheers.

Last edited by MeanDumpsterCat; 14th Sep 2020 at 2:03 pm.
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Old 14th Sep 2020, 2:38 pm   #2
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Default Re: Ferrograph Series 5 Triggering RCD

** forgot to put it in my original post but I know there's an EZ80 rectifier valve on the power supply. I'm thinking that would be a good place to start.
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Old 14th Sep 2020, 2:45 pm   #3
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Default Re: Ferrograph Series 5 Triggering RCD

The rectifier shouldn't cause the RCD to trip.

Remove the rectifier and unplug P3 from SK3, if the RCD still trips then suspect the mains transformers primary circuit including the transformer itself, if the RCD doesn't trip suspect the motor circuits including the motors themselves.

Lawrence.
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Old 14th Sep 2020, 3:53 pm   #4
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Default Re: Ferrograph Series 5 Triggering RCD

Okay, i'll give that a try.

Though i'm still puzzled as to why it was working when connected to my variac.
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Old 14th Sep 2020, 4:07 pm   #5
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Default Re: Ferrograph Series 5 Triggering RCD

Okay, I removed the rectifier and disconnected P3 and powered it on. RCD didnt trip. Are there any suspect parts in the motor circuit I should test for shorts (apart from the motors themselves of course)
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Old 14th Sep 2020, 4:19 pm   #6
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Default Re: Ferrograph Series 5 Triggering RCD

For components then apart from the motors, C4 and switches, there's nothing else that I can see looking at the manual I have.

Lawrence.
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Old 14th Sep 2020, 4:46 pm   #7
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Default Re: Ferrograph Series 5 Triggering RCD

I probed the terminals of C4 with my meter and it didnt show up as a short (unless i'm doing something wrong). I'll test some of the other switches but I think i'm going to have a break now and go back to it in a few days. I'll keep this thread updated.
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Old 14th Sep 2020, 4:51 pm   #8
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Default Re: Ferrograph Series 5 Triggering RCD

I mentioned C4 because looking at a photo in the manual its case appears to be earthed.

Lawrence.
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Old 14th Sep 2020, 4:58 pm   #9
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Default Re: Ferrograph Series 5 Triggering RCD

Oh okay. I didnt actually realise it was earthed. So i'll check between the terminals and the earth point.
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Old 14th Sep 2020, 5:41 pm   #10
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Default Re: Ferrograph Series 5 Triggering RCD

It may be worth checking that no one has subsequently added suppressors from the motors to earth.
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Old 14th Sep 2020, 7:32 pm   #11
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Default Re: Ferrograph Series 5 Triggering RCD

Okay, ive done a little more testing.

I noticed that all the poles on the main selector switch are shorted to ground. Pulling down the run lever doesnt seem to do anything. Any ideas?
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Old 14th Sep 2020, 8:06 pm   #12
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Default Re: Ferrograph Series 5 Triggering RCD

Disregard this. The switch is fine.

Still a little stumped on this one.
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Old 14th Sep 2020, 8:15 pm   #13
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Default Re: Ferrograph Series 5 Triggering RCD

According to the schematic only the pole of S1-2b is permanently connected to ground, the pole of S1-3a is switched to ground except when Record is selected, so something's amiss there.

EDIT: Whoops...post crossed.

Lawrence.
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Old 14th Sep 2020, 8:25 pm   #14
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Default Re: Ferrograph Series 5 Triggering RCD

I noticed that both of the connections on the erase head are shorted to ground, regardless of the position of the main switch ...
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Old 14th Sep 2020, 11:02 pm   #15
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Default Re: Ferrograph Series 5 Triggering RCD

Update: I think that C3 which goes between the erase head and ground is potentially short. I'll de-solder it tomorrow and double check.
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Old 15th Sep 2020, 3:16 pm   #16
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Default Re: Ferrograph Series 5 Triggering RCD

Okay, I tested C3 with my old analog multimeter and that seems to be okay. I dont have a meter that can measure capacitance but the needle jumps up briefly then goes back to zero.

I traced the connections on the schematic and I think that C4 (the large canned capacitor on the motor run circuit has shorted. I know this one will be a little more difficult to replace so my question is, would I be able to power up the machine with that capacitor disconnected just to see if the breaker still pops or would I potentially damage something?

Am I also right in assuming C4 is a paper capacitor and thus does not have polarity?

Cheers.
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Old 15th Sep 2020, 3:48 pm   #17
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Default Re: Ferrograph Series 5 Triggering RCD

If you disconnect C4 the capstan motor will not self start though it should run up at reduced power if you spin it by hand.

You are correct about it not being polarised.
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Old 15th Sep 2020, 4:23 pm   #18
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Default Re: Ferrograph Series 5 Triggering RCD

Thanks. I'll give it a try once I find a more usable soldering iron *sigh*.
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Old 15th Sep 2020, 4:35 pm   #19
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Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by MeanDumpsterCat View Post
Okay, I tested C3 with my old analog multimeter and that seems to be okay. I dont have a meter that can measure capacitance but the needle jumps up briefly then goes back to zero.
I assume you mean jumps back to zero on the voltage/current scale, not the resistance scale. A good capacitor out of circuit should read very high on the analogue meter resistance scale and should not jump much at all.

Quote:
Am I also right in assuming C4 is a paper capacitor and thus does not have polarity?
Yes C4 is paper, modern replacements will be Metallized Polypropylene.

The manual I am looking at lists it as 0.75uF for 240 volts Model 5A machine, what is your exact model ?

If you have to replace it, make sure the replacement is rated for continuous AC operation and suitable for motor run use.

David
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Old 15th Sep 2020, 4:41 pm   #20
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Default Re: Ferrograph Series 5 Triggering RCD

It's the capacitor charging due to the meter's battery voltage.

EDIT: Post crossed.

Lawrence.
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