UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players

Notices

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

Closed Thread
 
Thread Tools
Old 15th Sep 2020, 4:41 pm   #21
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by DMcMahon View Post
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.

David
Yeah that's what I meant.
Its stays high on the resistance scale but briefly decreases and goes back up again. This was tested out of circuit. But I dont think C3 is the cause of the problem (although I still think it needs replacing). C4 seems to be the one which is a completely dead short.
MeanDumpsterCat is offline  
Old 15th Sep 2020, 4:52 pm   #22
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by ms660 View Post
It's the capacitor charging due to the meter's battery voltage.

EDIT: Post crossed.

Lawrence.
Depends upon the capacitor value/voltage rating and the meter battery voltage, there will be minimal capacitor charging showing on the meter for many higher voltage capacitors on an analogue meter like an AVO.

David
DMcMahon is offline  
Old 15th Sep 2020, 4:56 pm   #23
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Ferrograph Series 5 Triggering RCD

The capacitors voltage rating won't affect things.

Lawrence.
ms660 is offline  
Old 15th Sep 2020, 5:37 pm   #24
barrymagrec
Octode
 
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,552
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by MeanDumpsterCat View Post
Quote:
Originally Posted by DMcMahon View Post
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.

David
Yeah that's what I meant.
Its stays high on the resistance scale but briefly decreases and goes back up again. This was tested out of circuit. But I dont think C3 is the cause of the problem (although I still think it needs replacing). C4 seems to be the one which is a completely dead short.
If you are measuring C4 in circuit you are actually measuring the motor winding which will be quite low. Faulty or not C4 will not cause your breaker to blow unless it is leaky to it`s case.
barrymagrec is offline  
Old 15th Sep 2020, 5:54 pm   #25
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by DMcMahon View Post
Quote:
Originally Posted by MeanDumpsterCat View Post

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

Cheers.
Yes C4 is paper, modern replacements will be Metalized 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

Been looking around for replacement capacitors.
Would these be a suitable replacement?
https://www.ebay.co.uk/itm/CBB61-mot...wAAOSwYTpdPbVI

Just a bit thrown off because of the different shape.
MeanDumpsterCat is offline  
Old 15th Sep 2020, 5:56 pm   #26
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by barrymagrec View Post
Quote:
Originally Posted by MeanDumpsterCat View Post
Quote:
Originally Posted by DMcMahon View Post

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.

David
Yeah that's what I meant.
Its stays high on the resistance scale but briefly decreases and goes back up again. This was tested out of circuit. But I dont think C3 is the cause of the problem (although I still think it needs replacing). C4 seems to be the one which is a completely dead short.
If you are measuring C4 in circuit you are actually measuring the motor winding which will be quite low. Faulty or not C4 will not cause your breaker to blow unless it is leaky to it`s case.
It is leaking to the case. Going from the connectors to the case results in a short.
MeanDumpsterCat is offline  
Old 15th Sep 2020, 6:16 pm   #27
barrymagrec
Octode
 
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,552
Default Re: Ferrograph Series 5 Triggering RCD

There you go then.
barrymagrec is offline  
Old 17th Sep 2020, 12:29 pm   #28
flywheel
Tetrode
 
Join Date: Aug 2005
Location: Leicester, Leicestershire, UK.
Posts: 68
Default Re: Ferrograph Series 5 Triggering RCD

Quote:
Originally Posted by MeanDumpsterCat View Post
It is leaking to the case. Going from the connectors to the case results in a short.
If you're measuring C4 in place, wired to the motor and strapped to the frame - and therefore with the can grounded - I'd suggest checking it out of circuit: A rare fault with Ferrograph capstan motors, but one I've encountered twice, is a short from one of the top loops at the corners of the stator winding to one of the alu spacers next to it (later versions of the motor have insulating sleeves over the top spacers to prevent this). If there's a breakdown between the winding and motor frame on your deck then it could be the motor shorting to ground, not the capacitor.

PS if the stator does have a short, I have a spare i can send you for the postage cost.
__________________
Andrew B.

Last edited by flywheel; 17th Sep 2020 at 12:42 pm. Reason: Additions and clarifications.
flywheel is offline  
Old 18th Sep 2020, 12:45 am   #29
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Thanks. I'll keep that in mind. I'll get around to removing it soon. Here's hoping it's just the capacitor though
MeanDumpsterCat is offline  
Old 18th Sep 2020, 1:41 am   #30
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Okay, just tested the motor run cap out of circuit and it seems to be fine. Or at least not shorted. Hmm..

The motors seem to still have resistance too.

Might have to go over the schematics again and see what I can spot.

What points on the motor do I need to test between?
MeanDumpsterCat is offline  
Old 18th Sep 2020, 9:58 pm   #31
flywheel
Tetrode
 
Join Date: Aug 2005
Location: Leicester, Leicestershire, UK.
Posts: 68
Default Re: Ferrograph Series 5 Triggering RCD

I'd suggest testing for leakage between the motor connections and the motor frame.
__________________
Andrew B.
flywheel is offline  
Old 18th Sep 2020, 10:24 pm   #32
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Cheers i'll give that a try. If it's not a complete short is there any amount of resistance which should be considered normal?

Sorry for the basic questions, i've not really dealt with motors before.
MeanDumpsterCat is offline  
Old 19th Sep 2020, 1:37 pm   #33
flywheel
Tetrode
 
Join Date: Aug 2005
Location: Leicester, Leicestershire, UK.
Posts: 68
Default Re: Ferrograph Series 5 Triggering RCD

Hi, no problem - there should be full insulation between the motor frame and any of the connector plug/solder tag points.
__________________
Andrew B.
flywheel is offline  
Old 20th Sep 2020, 3:06 pm   #34
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Okay,
So I tried measuring between one of the points which was connected to the motor run capacitor and the motor frame. The meter didnt read infinity but it was not at zero. I then tested the machine again and the fault is still there.

After that I measured the same two points again and the meter almost read infinity (needle moves just barely a fraction). I tried rotating the motor by hand to see if the position of the motor had any bearing on it and it didnt.

Then just for good measure, I tried it again after doing the second test after the meter read almost infinity (just to see if it had magically fixed itself) and yep, no luck still.

Getting a bit stuck for ideas ...

Pictures attached are from the first test.

On the second test the needle was almost, but not entirely on infinity.

I should point out that I powered on the machine with the motor disconnected from the capacitor and it still tripped.
Attached Thumbnails
Click image for larger version

Name:	2020-09-20 15.00.16.jpg
Views:	36
Size:	75.3 KB
ID:	216046   Click image for larger version

Name:	2020-09-20 15.00.22.jpg
Views:	44
Size:	68.1 KB
ID:	216047  
MeanDumpsterCat is offline  
Old 20th Sep 2020, 3:44 pm   #35
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

** Update **

Tested it again and there is definitly some leakage between the motor run wires and the motor frame / ground.

I think my meter must have been playing up. I done the exact same test again and this time it shows an almost dead short. For a sanity check I also tried my newer digital meter.

Pictures below.

I'm guessing that because of this a short still exists between two other points as it should have powered up fine without these wires connected.
Attached Thumbnails
Click image for larger version

Name:	2020-09-20 15.39.44.jpg
Views:	41
Size:	33.3 KB
ID:	216058   Click image for larger version

Name:	2020-09-20 15.39.47.jpg
Views:	47
Size:	64.3 KB
ID:	216059   Click image for larger version

Name:	2020-09-20 15.43.37.jpg
Views:	40
Size:	56.6 KB
ID:	216060  
MeanDumpsterCat is offline  
Old 20th Sep 2020, 4:23 pm   #36
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,191
Default Re: Ferrograph Series 5 Triggering RCD

If you have 1.3kOhms resistance between the motor windings and the chassis (at the voltage used by a normal digital multimeter, a few volts at most) then you have a fault. Even if that leak doesn't get any worse as the voltage increases and stays at 1.3k, it's going to pass a couple of hundred mA at mains voltage. That will trip an RCD (and with good reason, it's far too high a leakage current to be safe).

I am not sure what the legal requirements are, but I would want a resistance of several megohms at a test voltage of 500V (twice mains). A proper insulation tester is a somewhat specialised instument but actually you have one. The Mohm position of that BT tester (knob fully clockwise) does a test between the ''B' socket (or the 'A' socket if you press the button) and the ground socket at about 110V. That's not really enough, but better than the 2V of a digital multimeter.

I think you need to disconnect things and test some more. For example, disconnect all wires from that motor (note where they go!) and do an test between the motor connections and the motor frame. Any significant leakage (<10Mohms say) means you need a rewind.
TonyDuell is online now  
Old 20th Sep 2020, 4:54 pm   #37
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Thanks for the help. I'll try and test the motor out of circuit (its a bit of a big job to remove all of those connections.

I am also a little suspicious of the motor run switch since it seems to me like it could be short. Though it's not leaking to ground so that would cause the break. Likely would just cause the motors to run all the time if anything.

(I knew that old multimeter would come in handy some day )
MeanDumpsterCat is offline  
Old 20th Sep 2020, 7:32 pm   #38
flywheel
Tetrode
 
Join Date: Aug 2005
Location: Leicester, Leicestershire, UK.
Posts: 68
Default Re: Ferrograph Series 5 Triggering RCD

Looks like you've done the hard part by unsoldering the capacitor leads. The other two connections are by a plug, which is most easily got at after you undo the four motor-frame retaining screws (keep hold of the motor while you take the last two out), and then gently drop the motor by about half an inch. The plug is then easy to get at, but have a small screwdriver handy to lever it off the connector in case it's hard to unplug by hand.
__________________
Andrew B.
flywheel is offline  
Old 20th Sep 2020, 7:51 pm   #39
MeanDumpsterCat
Pentode
 
MeanDumpsterCat's Avatar
 
Join Date: Oct 2014
Location: Selsey, West Sussex, UK.
Posts: 204
Default Re: Ferrograph Series 5 Triggering RCD

Oh okay. I didnt realise it was connected via a plug. That makes life easier.

I'll test it any keep the thread updated.
MeanDumpsterCat is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:39 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.