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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 18th Jun 2021, 12:34 pm   #1
Jonorangesky
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Default Ferrograph series 6 no sound

I had my Ferrograph series 6 go for a full service in November 2010. I stored the unit away and then moved home. Yesterday, so over 10 years later, I switched it on for the first time since the service!
The transport works great. However, there is no sound at all. I opened it up and the valves are glowing.
Can anyone think of a fault that would occur to a fully serviced unit just by being left stored (in a centrally heated house) for 10 years?
I note on the service list it says capacitor 22mf 450v was changed - I guess that is the infamous capacitor that must always be changed on this model.
The service also says 'smoothing capacitors changed'
Regards
Jon
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Old 18th Jun 2021, 4:43 pm   #2
Vintage Engr
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Default Re: Ferrograph series 6 no sound

Hi Jon, welcome to the forum.

It could be something simple. The internal speaker is fed via the 'break' connections on the 'ext L/S' jack socket. After long storage they could possibly be tarnished. Just inserting a plug in & out a few times might temporarily clear it. Also there is a switch, SW7, which mutes the internal speaker. It could be in the wrong position, or just dirty.

The other possibility is that when the unit was repaired, that the internal speaker wasn't plugged back in to the internal plug/socket 'SK6 on the amplifier chassis. It would still operate with an external speaker.

There is no internal HT fuse, although some users have retrofitted one, so it's unlikely to be that.

David.
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Old 19th Jun 2021, 7:45 pm   #3
DMcMahon
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Default Re: Ferrograph series 6 no sound

Quote:
Originally Posted by Jonorangesky View Post
I note on the service list it says capacitor 22mf 450v was changed - I guess that is the infamous capacitor that must always be changed on this model.
The service also says 'smoothing capacitors changed'

Not familiar with any specific capacitor that should be changed on the Series 6.

The 22mF capacitor reference is probably 22uF (22 Micro Farads), mf being an old reference for uF. However cannot see a 22uF on the Series 6 schematic I am looking at.

Old capacitors do degrade and occasionally actually fail but not common for a bad capacitor to cause complete loss of sound, so Davids suggestions above should be checked out fully.

The schematic shows a dual can 16uF +16uF 350V electrolytic capacitor (C33 + C34) for the reservoir and main smoothing/filter capacitor, this is in the power unit. Also a triple can electrolytic capacitor 8uF +16uF+16uF 350V (C6, C7 & C19) in the amplifier unit for further HT smoothing and de-coupling.

One type of capacitor that is often recommended to be checked/changed is the grid coupling capacitor, particularly the capacitor coupling to the control grid of the output valve (V4 an EL84 Pentode in your machine) that drives the internal loudspeaker via an output transformer. On your schematic it is C22, a 0.047uF 400V.

However the grid coupling capacitor is normally only a potential issue when the capacitor is paper electrolyte type. The parts listing for the Series 6 lists the grid coupling capacitors as Polyester, which generally are unlikely to be problematic.

David

Last edited by Cobaltblue; 19th Jun 2021 at 9:25 pm. Reason: Fixed quote
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Old 19th Jun 2021, 8:08 pm   #4
DMcMahon
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Default Re: Ferrograph series 6 no sound

If nothing is found bad when you check out Davids suggestions from Post 2 then would recommend as a first test to measure the main HT voltage.

Only do this is you are competent and can do it safely. You can measure the main HT supply at C34 & C33 the dual can capacitor in the Power Unit. Values in Playback mode listed in the manual are +285V at C34 (input to smoothing choke L5) and +275V at C33 (output of L5). These are DC voltages with the -ve lead of the test meter being connected to ground/chassis/earth. Values listed are just ball park values.

If you do measure any voltages then for good measure would be worthwhile measuring the control grid/g1 of the EL84 output pentode (pin 2) to make sure the grid coupling capacitor C22 is good (not leaky/not passing DC voltage), there should be no +ve voltage at pin 2.

David
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Old 21st Jun 2021, 3:54 pm   #5
DMcMahon
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Default Re: Ferrograph series 6 no sound

Noticed that there is another triple (16uF+16uF+16uF 350V) can electrolytic capacitor in the Amplifier unit, C20, C32 & C38, once again for HT smoothing.

David
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Old 22nd Jun 2021, 7:00 pm   #6
Uncle Bulgaria
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Default Re: Ferrograph series 6 no sound

Jonorangesky - let's hear about the obvious things first, as mentioned by Vintage Engr. Is the loudspeaker plug inserted into its socket? If you have the unit in 'play' (even without a tape loaded and playing) and turn up the gain to full, is there a hum from the loudspeaker?
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Old 25th Jun 2021, 9:41 pm   #7
reelguy
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Default Re: Ferrograph series 6 no sound

There are four models in the series Six Possibly more if YD models ?. If I remember correctly. 631 Mono 2 track . 633 Mono 2 track with third head for monitoring , 632 2 track Stereo , 634 4 track Stereo . The two Stereo models have a Mono transistor monitor amp . The Mono M/cs have built in valve amps.
i have a Ferrograph Series Six Stereo m/c but it is missing the transistor amp so I also don't have sound . The previous owner messed about with the wiring. One day I will get round to checking it out.
Peter W Reelguy .
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