Help identifying PAM radio (TB61) - UK Vintage Radio Repair and Restoration Discussion Forum

Northyorks1 · 23rd Nov 2020, 4:45 pm

Can anyone identify this pam radio please, have had a look around but could only find a picture, but no model number or details.

Ian

FIXITNOW · 23rd Nov 2020, 4:53 pm

look like the same board as in the Ekco PT378 and many others

Northyorks1 · 23rd Nov 2020, 6:00 pm

Yes I did notice that, I have a PT378 and also PYE Q8 with same chassis.

Ian

AC/HL · 23rd Nov 2020, 8:52 pm

Different distribution chains, same with Thorn group brands and the other major manufacturers.

Paul_RK · 23rd Nov 2020, 9:21 pm

Seems it's a TB61, not a variant I've ever met in the flesh.

https://www.vintage-radio.net/forum/....php?p=1165798

Paul

Northyorks1 · 24th Nov 2020, 1:40 am

Thanks very much Paul.

Ian

Northyorks1 · 24th Nov 2020, 2:10 am

Looking at the chassis in Pamphonicas thread, the two transistors he mentions are different on my chassis without the heatsink. Have the transistors been changed?

Ian

Paul_RK · 24th Nov 2020, 2:29 am

These models appear sometimes with Pye's own Newmarket transistors and sometimes with Mullard types. The other four in your set have the distinctive cans of Newmarket devices, but I can't identify that output pair. Any readable type numbers and/or branding on them?

Paul

Northyorks1 · 24th Nov 2020, 3:33 am

TH 2N 322 on transistors, and also I think its either a 7 or L and 0.

Ian

Herald1360 · 24th Nov 2020, 11:54 am

2N322 is a PNP Ge device similar (slightly beefier) to an OC72 so very likely replacements at some time. Doubtful that they would be original.

NKT251 is itself a bit beefier than the 2N322, 300mW vs 225mW.

OC81 would be better (600mW). AC128 would have been go to but for tin whiskers waving about...

Northyorks1 · 24th Nov 2020, 1:16 pm

Thanks for info Herald1360.

Ian

AC/HL · 24th Nov 2020, 3:49 pm

Does the soldering look original? There were supply problems in the early days, but that usually meant fitting Mullards rather than the originally specified type.

Paul_RK · 24th Nov 2020, 5:52 pm

Yes, I do believe I've seen (it may even be here) a Pye P123BQ with a full set of RCA transistors, almost certainly from new.

Paul

Northyorks1 · 24th Nov 2020, 5:59 pm

No solder does not look origininal, and also not original in a number of other places. I have also noticed that the capacitor marked C20 on Pamphonicas chassis is missing on my chassis.

Ian

Northyorks1 · 25th Nov 2020, 1:28 pm

I was just looking through the Ekco pt378 schematic and it mentions the process for changing from Mullard to Newmarket transistors, and it mentions C20 being ommited along with other parts. Which could explain why C20 is missing on my Pam chassis. I get the impression that this is if you change all transistors, but only the two NKT251 have been changed on my chassis. Bit confusing.

Ian

23rd Nov 2020, 4:45 pm	#1
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Help identifying PAM radio (TB61) Can anyone identify this pam radio please, have had a look around but could only find a picture, but no model number or details. Ian Attached Thumbnails

23rd Nov 2020, 4:53 pm	#2
FIXITNOW Octode Join Date: Feb 2007 Location: Ely, Cambridgeshire, UK. Posts: 1,976	Re: Help identifying PAM radio look like the same board as in the Ekco PT378 and many others

23rd Nov 2020, 6:00 pm	#3
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio Yes I did notice that, I have a PT378 and also PYE Q8 with same chassis. Ian

23rd Nov 2020, 8:52 pm	#4
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Help identifying PAM radio Different distribution chains, same with Thorn group brands and the other major manufacturers.

23rd Nov 2020, 9:21 pm	#5
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,256	Re: Help identifying PAM radio Seems it's a TB61, not a variant I've ever met in the flesh. https://www.vintage-radio.net/forum/....php?p=1165798 Paul

24th Nov 2020, 1:40 am	#6
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) Thanks very much Paul. Ian

24th Nov 2020, 2:10 am	#7
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) Looking at the chassis in Pamphonicas thread, the two transistors he mentions are different on my chassis without the heatsink. Have the transistors been changed? Ian Attached Thumbnails

24th Nov 2020, 2:29 am	#8
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,256	Re: Help identifying PAM radio (TB61) These models appear sometimes with Pye's own Newmarket transistors and sometimes with Mullard types. The other four in your set have the distinctive cans of Newmarket devices, but I can't identify that output pair. Any readable type numbers and/or branding on them? Paul

24th Nov 2020, 3:33 am	#9
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) TH 2N 322 on transistors, and also I think its either a 7 or L and 0. Ian

24th Nov 2020, 11:54 am	#10
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Help identifying PAM radio (TB61) 2N322 is a PNP Ge device similar (slightly beefier) to an OC72 so very likely replacements at some time. Doubtful that they would be original. NKT251 is itself a bit beefier than the 2N322, 300mW vs 225mW. OC81 would be better (600mW). AC128 would have been go to but for tin whiskers waving about... __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

24th Nov 2020, 1:16 pm	#11
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) Thanks for info Herald1360. Ian

24th Nov 2020, 3:49 pm	#12
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Help identifying PAM radio (TB61) Does the soldering look original? There were supply problems in the early days, but that usually meant fitting Mullards rather than the originally specified type.

24th Nov 2020, 5:52 pm	#13
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,256	Re: Help identifying PAM radio (TB61) Yes, I do believe I've seen (it may even be here) a Pye P123BQ with a full set of RCA transistors, almost certainly from new. Paul

24th Nov 2020, 5:59 pm	#14
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) No solder does not look origininal, and also not original in a number of other places. I have also noticed that the capacitor marked C20 on Pamphonicas chassis is missing on my chassis. Ian

25th Nov 2020, 1:28 pm	#15
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 623	Re: Help identifying PAM radio (TB61) I was just looking through the Ekco pt378 schematic and it mentions the process for changing from Mullard to Newmarket transistors, and it mentions C20 being ommited along with other parts. Which could explain why C20 is missing on my Pam chassis. I get the impression that this is if you change all transistors, but only the two NKT251 have been changed on my chassis. Bit confusing. Ian