Pye 39J/H, I.F instability/whistle. - UK Vintage Radio Repair and Restoration Discussion Forum

johnlees · 1st Mar 2007, 9:29 pm

This radio works fine on all wavebands but there is an annoying whistle as you tune through stations (all wavebands). As you get nearer to each station the whistle decreases in frequency, disappears on the station (just about) and then re-appears and increases in frequency the other side of the station.
It's very pronounced and annoying. It's so bad on medium wave that only the main BBC stations can really be listened to.

What's the cause, please, and how do I cure it? I have the circuit diagram.

renato_enca · 1st Mar 2007, 9:36 pm

hmm...that sounds like there's a "beat oscillator" in the radio, the ones used in some amateur receivers...may be the IF amplifier oscillating...

Steve_P · 1st Mar 2007, 9:36 pm

This is beating at I.F. somewhere. Look at De-coupling and Coupling Caps on the I.F. Stage.

Cheers,

Steve P

mickjjo · 1st Mar 2007, 9:43 pm

Hi John, I believe this set uses those red Mullard 'E' series valves, so check that the metalising is earthed properly, particularly the EF39, as bad contact can cause IF instability which results in the symptoms described. Binding the valve with fuse wire and connecting to the relevent pin usually works.

Regards, Mick.

johnlees · 1st Mar 2007, 9:55 pm

Thanks Renato, Steve and Mick. Yes, indeed it does use those red metalized valves and the coating on three of them looks very bad indeed near their bases.
I will have a closer look tomorrow.

johnlees · 1st Mar 2007, 10:12 pm

Yep, the EF39 coating is supposed to connect to Pin 1 but it doesn't ! It's missing round the bottom 1/8 inch of the valve (as it is on a couple of other valves). I can only connect my meter to it by scraping off more red, so I'll do that and try the fusewire trick.

Pin 1 on the valveholder connects direct to chassis, so could I take a wire from the fusewire wrapped round the (scraped) valve coating to any chassis point near the valve?

johnlees · 1st Mar 2007, 10:22 pm

I'm a dum-dum ! It is the red coating that is the metalizing I've just realised ! Sorry to be so dim ! Working on it now.

Sideband · 1st Mar 2007, 10:23 pm

Yes that was a common way of doing a repair on these valves. Wind the fusewire round the base of the valve and then run the end down the side of the base to pin 1. You will probably need to give the pin a quick touch with a file to get down to the copper.

As others have said, it's also worth checking decouplers.

Good luck!

Rich.

johnlees · 1st Mar 2007, 10:33 pm

Metalizing on EF39 (I.F. amp) definitely earthed now but problem disappointingly remains.
I will tackle the other valves similarly tomorrow and report back but for now it's a

to drown my sorrows.

johnlees · 1st Mar 2007, 10:35 pm

Thanks for that, Richard. That is what I will do.

paulsherwin · 1st Mar 2007, 10:35 pm

Don't forget obvious things like interference from TVs and computer monitors. It may be coming from next door

Paul

johnlees · 1st Mar 2007, 10:41 pm

Thanks, Paul. No, my computer wasn't on and in any case I've tried my other three radios in the same room and they're all working properly.

Sideband · 1st Mar 2007, 11:03 pm

Quote:

Originally Posted by johnlees

Metalizing on EF39 (I.F. amp) definitely earthed now but problem disappointingly remains.

Decouplers are the next thing then. It could also be an alignment problem. Not IF...probably aerial circuits. If they are way out of line either by a component fault or mal-adjustment, there could be second-channel interference. What happens is the aerial circuit is unable to reject the unwanted signals at plus and minus IF frequency so you get a beat note during tuning.

Hopefully it will be nice and simple though!

Rich.

jjl · 2nd Mar 2007, 1:40 am

Quote:

Originally Posted by johnlees

Metalizing on EF39 (I.F. amp) definitely earthed now but problem disappointingly remains.

Agree that decoupling especially on the AVC line is a likely suspect. However, I've experienced this sort of problem where an EF39 is used for the IF amp even when the metallising is sound; it may be worth trying out a swap of the RF and IF amp. EF39s or substituting another.

John

johnlees · 2nd Mar 2007, 11:05 am

All done ! Cured and working properly ! And I've got a red face because initially I jumped to a wrong conclusion and didn't spot there were TWO EF39s. Initially I "fusewired" the RF amp. to no avail but on "fusewiring" the IF amp. everything is hunky-dory.

Many thanks for all your help. Regards, John.

1st Mar 2007, 9:29 pm	#1
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Pye 39J/H, I.F instability/whistle. This radio works fine on all wavebands but there is an annoying whistle as you tune through stations (all wavebands). As you get nearer to each station the whistle decreases in frequency, disappears on the station (just about) and then re-appears and increases in frequency the other side of the station. It's very pronounced and annoying. It's so bad on medium wave that only the main BBC stations can really be listened to. What's the cause, please, and how do I cure it? I have the circuit diagram. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 9:36 pm	#2
renato_enca Retired Dormant Member Join Date: Feb 2007 Location: Lisbon, Portugal Posts: 51	Re: Pye 39J/H with annoying whistle. hmm...that sounds like there's a "beat oscillator" in the radio, the ones used in some amateur receivers...may be the IF amplifier oscillating...

1st Mar 2007, 9:36 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Pye 39J/H with annoying whistle. This is beating at I.F. somewhere. Look at De-coupling and Coupling Caps on the I.F. Stage. 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...?

1st Mar 2007, 9:43 pm	#4
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Pye 39J/H with annoying whistle. Hi John, I believe this set uses those red Mullard 'E' series valves, so check that the metalising is earthed properly, particularly the EF39, as bad contact can cause IF instability which results in the symptoms described. Binding the valve with fuse wire and connecting to the relevent pin usually works. Regards, Mick.

1st Mar 2007, 9:55 pm	#5
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. Thanks Renato, Steve and Mick. Yes, indeed it does use those red metalized valves and the coating on three of them looks very bad indeed near their bases. I will have a closer look tomorrow. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 10:12 pm	#6
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. Yep, the EF39 coating is supposed to connect to Pin 1 but it doesn't ! It's missing round the bottom 1/8 inch of the valve (as it is on a couple of other valves). I can only connect my meter to it by scraping off more red, so I'll do that and try the fusewire trick. Pin 1 on the valveholder connects direct to chassis, so could I take a wire from the fusewire wrapped round the (scraped) valve coating to any chassis point near the valve? __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 10:22 pm	#7
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. I'm a dum-dum ! It is the red coating that is the metalizing I've just realised ! Sorry to be so dim ! Working on it now. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 10:23 pm	#8
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,580	Re: Pye 39J/H with annoying whistle. Yes that was a common way of doing a repair on these valves. Wind the fusewire round the base of the valve and then run the end down the side of the base to pin 1. You will probably need to give the pin a quick touch with a file to get down to the copper. As others have said, it's also worth checking decouplers. Good luck! Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

1st Mar 2007, 10:33 pm	#9
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. Metalizing on EF39 (I.F. amp) definitely earthed now but problem disappointingly remains. I will tackle the other valves similarly tomorrow and report back but for now it's a to drown my sorrows. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 10:35 pm	#10
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. Thanks for that, Richard. That is what I will do. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

1st Mar 2007, 10:35 pm	#11
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Pye 39J/H with annoying whistle. Don't forget obvious things like interference from TVs and computer monitors. It may be coming from next door Paul

1st Mar 2007, 10:41 pm	#12
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. Thanks, Paul. No, my computer wasn't on and in any case I've tried my other three radios in the same room and they're all working properly. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)

2nd Mar 2007, 11:05 am	#15
johnlees Hexode Join Date: Oct 2004 Location: Cheltenham, Gloucestershire, UK. Posts: 283	Re: Pye 39J/H with annoying whistle. All done ! Cured and working properly ! And I've got a red face because initially I jumped to a wrong conclusion and didn't spot there were TWO EF39s. Initially I "fusewired" the RF amp. to no avail but on "fusewiring" the IF amp. everything is hunky-dory. Many thanks for all your help. Regards, John. __________________ Now that's the kind of Long Wave I like ! (Severn Bore near Gloucester)