Ferguson 625U making a twanging noise - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Steve_P · 26th Jan 2007, 10:48 pm

Modifications section of my copy of the Trader Sheet says:

In later models, a capacitor, 7pF, is connected between pins 2 and 7 (Control Grid and Anode) of V5.

A capacitor 100pf is connected between control grid V4d and Chassis.

I wonder why these were added. Maybe if you added them to yours, it may help matters?

Cheers,

Steve P

stephanie · 27th Jan 2007, 7:14 am

Nothing...nothing nothing works.

Every single mod suggested, every component suggested.....tested, changed, etc. No dice.

Steve_P · 27th Jan 2007, 2:48 pm

OK, well I'd put the old UL84 back in and see what happens....

Or, try something daft like replacing that blue wire with microphone wire (screened and link the screen to earth!) and see if that gets rid of the noise!

Cheers,

Steve P

stephanie · 29th Jan 2007, 3:49 pm

Quote:

Originally Posted by Steve_P

Or, try something daft like replacing that blue wire with microphone wire (screened and link the screen to earth!) and see if that gets rid of the noise!

Cheers,

Steve P

Screening the blue wire didn't help.

But I've got another daft idea. Considering the noise has now turned into a crackle-pop with distorted sound, I'm wondering if the heat has caused the PCB to develop carbon tracks.

So I figure if I raise the socket off the board and make some of the connections in mid-air, I might be able to fix it?

I got the idea from this page:

http://www.cs.uu.nl/~gerard/RadioCor...ts/Ko23621.htm

While it's not exactly the same tubes...the situation almost seems the same - except that it doesn't take five minutes for the problem to appear. More like five or ten seconds.

I'm out of options at this point.....so...I certainly have nothing to lose...

Steve_P · 29th Jan 2007, 4:24 pm

That looks stupid, but if it works, then great. But what if it doesn't?

Look, if I send you my address, would you send me the set. I'm curious to say the least, and I've never had anything like that to do with any set I've fixed.

Besides, this thread has got me into hot water....

Cheers,

Steve P

stephanie · 29th Jan 2007, 4:36 pm

Well, if it doesn't, I can always undo what I did and put the socket back on the PC board as original.

I already managed to remove it without damaging the board, so its all a matter of attaching wires to the thing and then attach the other ends to the board.

Steve, if I do send you this bu-#@-r, is it OK if I just send you the board & speaker without the cabinet? Just to make shipping easier?

Sideband · 29th Jan 2007, 6:09 pm

Quote:

Originally Posted by stephanie

But I've got another daft idea. Considering the noise has now turned into a crackle-pop with distorted sound, I'm wondering if the heat has caused the PCB to develop carbon tracks.

It's not such a daft idea. It is not unknown for PCB's to develope leakage and carbon tracking....I had it on a little Stella set once that ended up as scrap...! In fact I think Paul (Stenning) describes a repair to a similar set somewhere on the site. In my case, the tracking was causing quite a high positive voltage to appear on the control grid of the output valve and the board was really too far gone to bother with.

The only thing you have to remember is that if you connect the valve base up using bits of wire and then simply connect the other ends of the wires back in the holes where the valveholder was, the leakage will still be there....if you see what I mean

. You really have to isolate the components from the PCB. I suggest you lift one-end of any component going to the valveholder off the PCB and then connect a wire from the valveholder to the relevant component. See what I mean? Messy but it will prove the point.

Rich.

Mike Phelan · 29th Jan 2007, 6:19 pm

Steph

The link shown has very long leads on the mod - not too good an idea.
OK to test it, though.

I had quite a few G6 CTVs that had conductive print (heater to grid, ISTR) on one of the 10-pin PCF200s giving a magenta/green hum bar. The cure was to remove the base and drill the affected print away, then do the same to the components connected to them, and wire it up on the print side.

HTH

PJL · 29th Jan 2007, 7:26 pm

Is it me or are the symptoms changing? Originally it was only in the case and with the tone control in certain positions, then when the blue wire was moved, then when the volume was turned up and now the sound has deteriorated further.

Intermittent connection springs to mind...PCB's and valves were never a good idea...why not leave the thing turned on and see if whatever it is finally fails altogether?

stephanie · 29th Jan 2007, 8:11 pm

No, it's not just you. It's just being erratic...period. The sound also seems to vary with the position of the tone and volume controls. Go figure.

stephanie · 3rd Feb 2007, 11:04 pm

A quick update. It seems like I managed to fix it.

I lifted the socket off the PC board and all the connections (except internals, grid-3 and filament) were done in the air. A little bit of creative wire-dress was needed to completely eliminate the last of the twanging. Prodded a wire going near the mains connections into a 90 degree angle (good thing I used insulated solid wire) and that seems to have repaired it.

I have the set playing out of the case right now....and it seems to be doing just fine.

We'll see what happens when I put the dial scale & pointers and put it back in the cabinet....

stephanie · 5th Feb 2007, 2:34 am

Well. It's done and closed up. See new thread on "success stories"

https://www.vintage-radio.net/forum/...ad.php?t=14609

26th Jan 2007, 10:48 pm	#21
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Ferguson 625U making a twanging noise Modifications section of my copy of the Trader Sheet says: In later models, a capacitor, 7pF, is connected between pins 2 and 7 (Control Grid and Anode) of V5. A capacitor 100pf is connected between control grid V4d and Chassis. I wonder why these were added. Maybe if you added them to yours, it may help matters? Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

27th Jan 2007, 7:14 am	#22
stephanie Retired Dormant Member Join Date: Jul 2005 Location: New Bern, North Carolina, USA Posts: 346	Re: Ferguson 625U making a twanging noise Nothing...nothing nothing works. Every single mod suggested, every component suggested.....tested, changed, etc. No dice.

27th Jan 2007, 2:48 pm	#23
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Ferguson 625U making a twanging noise OK, well I'd put the old UL84 back in and see what happens.... Or, try something daft like replacing that blue wire with microphone wire (screened and link the screen to earth!) and see if that gets rid of the noise! Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

29th Jan 2007, 4:24 pm	#25
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Ferguson 625U making a twanging noise That looks stupid, but if it works, then great. But what if it doesn't? Look, if I send you my address, would you send me the set. I'm curious to say the least, and I've never had anything like that to do with any set I've fixed. Besides, this thread has got me into hot water.... Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

29th Jan 2007, 4:36 pm	#26
stephanie Retired Dormant Member Join Date: Jul 2005 Location: New Bern, North Carolina, USA Posts: 346	Re: Ferguson 625U making a twanging noise Well, if it doesn't, I can always undo what I did and put the socket back on the PC board as original. I already managed to remove it without damaging the board, so its all a matter of attaching wires to the thing and then attach the other ends to the board. Steve, if I do send you this bu-#@-r, is it OK if I just send you the board & speaker without the cabinet? Just to make shipping easier?

29th Jan 2007, 6:19 pm	#28
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Ferguson 625U making a twanging noise Steph The link shown has very long leads on the mod - not too good an idea. OK to test it, though. I had quite a few G6 CTVs that had conductive print (heater to grid, ISTR) on one of the 10-pin PCF200s giving a magenta/green hum bar. The cure was to remove the base and drill the affected print away, then do the same to the components connected to them, and wire it up on the print side. HTH __________________ Mike.

29th Jan 2007, 7:26 pm	#29
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 625U making a twanging noise Is it me or are the symptoms changing? Originally it was only in the case and with the tone control in certain positions, then when the blue wire was moved, then when the volume was turned up and now the sound has deteriorated further. Intermittent connection springs to mind...PCB's and valves were never a good idea...why not leave the thing turned on and see if whatever it is finally fails altogether?

29th Jan 2007, 8:11 pm	#30
stephanie Retired Dormant Member Join Date: Jul 2005 Location: New Bern, North Carolina, USA Posts: 346	Re: Ferguson 625U making a twanging noise No, it's not just you. It's just being erratic...period. The sound also seems to vary with the position of the tone and volume controls. Go figure.

3rd Feb 2007, 11:04 pm	#31
stephanie Retired Dormant Member Join Date: Jul 2005 Location: New Bern, North Carolina, USA Posts: 346	Re: Ferguson 625U making a twanging noise A quick update. It seems like I managed to fix it. I lifted the socket off the PC board and all the connections (except internals, grid-3 and filament) were done in the air. A little bit of creative wire-dress was needed to completely eliminate the last of the twanging. Prodded a wire going near the mains connections into a 90 degree angle (good thing I used insulated solid wire) and that seems to have repaired it. I have the set playing out of the case right now....and it seems to be doing just fine. We'll see what happens when I put the dial scale & pointers and put it back in the cabinet....

5th Feb 2007, 2:34 am	#32
stephanie Retired Dormant Member Join Date: Jul 2005 Location: New Bern, North Carolina, USA Posts: 346	Re: Ferguson 625U making a twanging noise Well. It's done and closed up. See new thread on "success stories" https://www.vintage-radio.net/forum/...ad.php?t=14609 Last edited by Paul Stenning; 5th Feb 2007 at 9:29 pm. Reason: Added link to success story