EKCO SRG 601. transformer - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

marty-radiogram · 13th Dec 2020, 3:51 pm

Thanks Graham, i have soldered in 2,2 ohm resistors and they are getting super hot
to the point of smoking, so now I am really stuck !!

when I got the radiogram these resistors were burnt in half
Any clues as what to do next , bar scrapping it.
thanks Martitn

Station X · 13th Dec 2020, 3:57 pm

I'm not a transistor man, but I expect another member will be able to assist you.

ms660 · 13th Dec 2020, 4:09 pm

There's a clue in the opening statement in Post#1

The output stage is DC coupled, all the transistors in that stage should be checked, if one checks duff I would replace the lot, also check the output coupling capacitor, I personally would replace the lot anyways, that's what most service techs would do.

Good luck whicheverways.

Lawrence.

marty-radiogram · 14th Dec 2020, 2:57 pm

Do you know what sort of transistors I should be buying please ?

I am a mech eng , on a learning curve !!

ms660 · 14th Dec 2020, 3:05 pm

Quote:

Originally Posted by marty-radiogram

Do you know what sort of transistors I should be buying please ?

I am a mech eng , on a learning curve !!

I'm not sure because I don't have the full service details but someone on the forum probably has.

EDIT: Having said the above, looking at a listing for that model on the radiomuseum website lists transistors that are prone to "tin whiskers" Search for that subject on this forum or on the web to get the info on that.

Lawrence.

Nuvistor · 14th Dec 2020, 3:32 pm

TR8,9,10 and 11 are audio amp and DC coupled.

Station X · 14th Dec 2020, 4:36 pm

The transistors to check and change are TR8, 9, 10 and 11 which are DC coupled.

Guide to testing transistors (out of circuit) here:-

https://www.vintage-radio.net/forum/...ad.php?t=42194

marty-radiogram · 16th Dec 2020, 10:41 am

I think I have found the transistors , 3 in copper heat sinks and one small one in the open, i someone could say yay or nay that would be great, whilst I try and buy some of these on eBay. please see pictures attached hopefully they are attached !!

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crackle · 16th Dec 2020, 11:00 am

Yes, remove all 4 transistors from that amp board, note down where they came from and how they were connected. Test them and replace any that show as faulty or suspect. You have the other amp board as a reference should you need it so leave the transistors in that one alone.
The red capacitor C81 400uF will need to be changed on both amp boards. That type are known to be unreliable and are probably the original cause for the transformer to burn out. The blue Philips electrolytics are normally OK.
What are the smoothing caps like C63, C64, C65, can you show a photo of them?

Dont forget to change those 2.2 Ohm resistors you replaced to the proper value of 2.2 ohm.

Mike

Station X · 16th Dec 2020, 11:14 am

I'll just add that the designation 'VT' (Valve Transistor) as in 'VT8' has been used on the PCB rather than the more common 'TR' (Transistor).

Be careful in identifying the leads of the new transistors and test them before fitting them.

marty-radiogram · 23rd Dec 2020, 11:01 pm

Evening,
I have received the transistors i ordered from eBay , but my problem now is
practical , even though I can identify each on the circuit diagram , i can't relate that to the real components because only one is identified on the PCB [vt8]

thus I am stuck again, any help would be fab, some photos attached
thanks yet again Martin

ms660 · 24th Dec 2020, 2:37 pm

The only schematic detail I have is the snippet in Post#13, based on that and the photo's in Post#31:

1st photo.....TR9.

2nd photo.....TR11 on the left and TR10 on the right.

3rd photo.....TR8.

The colour coding for the sleeves on TR9, TR10 and TR11:

White = Emitter.

Green = Base.

Red = Collector.

So far as I can make out.

Lawrence.

marty-radiogram · 30th Dec 2020, 12:35 pm

Morning hope everyone had a decent Christmas, considering....

I changed and tested the transistors on both RH AND LH boards
only one was dud on the RH pcb and one had come loose/unsoldered on the LH pcb.

So my next phase is to change those red capacitors which I think are
400uF 18V , but I can't find anyone selling them except Farnell who want
£25 quid to deliver a £3 quid part

is there anyone else selling these does anyone know ?
thanks in anticipation
Martin

Cobaltblue · 30th Dec 2020, 1:06 pm

Hi You can use 470uF 25V

The extra capacitance will be of little consequence and you should be able to find these much cheaper.

Cheers

Mike T

marty-radiogram · 4th Jan 2021, 5:58 pm

Afternoon all,
I have swapped out both red capacitors for 470uF 25V as per.
I must have done something wrong , the LH channel was fine.
But on the RH channel smoke poured off the insulation of the AC128 transistors , and the transistors are toast.
I have ordered some more . But what might I have done wrong ??
I am reluctant to give up .
thanks again everyone , Martin

Nuvistor · 4th Jan 2021, 7:58 pm

Double check the work you have done, perhaps a solder bridge on the print. Of course you could be just unlucky and the transistor whiskers shorted out inside the transistors as they are prone to do.

marty-radiogram · 13th Jan 2021, 5:18 pm

Afternoon,
& Eureka!!
I am happy to say thanks to everyones help on this forum, I have now got the
Ekco radiogram working , both channels ok now, and i have added a separate transformer for the lights.
And it looks really good too , I have now to get the record deck to work.

But to bring it into this century I want to add a Bluetooth input , so would anyone know where to break into the circuitry to add an audio Input ??
many thanks Martin

Edward Huggins · 13th Jan 2021, 6:01 pm

Quote:

Originally Posted by marty-radiogram

Afternoon,
& Eureka!!

And it looks really good too , I have now to get the record deck to work.

But to bring it into this century I want to add a Bluetooth input , so would anyone know where to break into the circuitry to add an audio Input ??
many thanks Martin

A great result. As to the record deck, the original fitted was a Garrard "Model 1000" and uses near indentical mechanics to the Garrard "Autoslim".

Michael Maurice · 13th Jan 2021, 8:24 pm

Quote:

Originally Posted by marty-radiogram

But to bring it into this century I want to add a Bluetooth input , so would anyone know where to break into the circuitry to add an audio Input ??
many thanks Martin

You don't have to break into anything, use the tape socket, you might need a 3.5mm stereo jack or phono to DIN lead.

marty-radiogram · 18th Jan 2021, 10:52 am

That's a great tip regarding the Tape Din socket , for Bluetooth.
I've dismantled the record deck and basically all the grease has turned to glue,
so I've cleaned it all up and re lubricated with new light grease and PTFE oil.
It all works well, except when on 33 rpm and auto changer mode ,when the record/LP
drops, the turntable nearly stops spinning, its fine on the higher speeds, does anyone know which bit of the mechanism might be causing this ?
thanks Martin

13th Dec 2020, 3:51 pm	#21
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Thanks Graham, i have soldered in 2,2 ohm resistors and they are getting super hot to the point of smoking, so now I am really stuck !! when I got the radiogram these resistors were burnt in half Any clues as what to do next , bar scrapping it. thanks Martitn

13th Dec 2020, 3:57 pm	#22
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: EKCO SRG 601. transformer I'm not a transistor man, but I expect another member will be able to assist you. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

13th Dec 2020, 4:09 pm	#23
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: EKCO SRG 601. transformer There's a clue in the opening statement in Post#1 The output stage is DC coupled, all the transistors in that stage should be checked, if one checks duff I would replace the lot, also check the output coupling capacitor, I personally would replace the lot anyways, that's what most service techs would do. Good luck whicheverways. Lawrence.

14th Dec 2020, 2:57 pm	#24
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Do you know what sort of transistors I should be buying please ? I am a mech eng , on a learning curve !!

14th Dec 2020, 3:32 pm	#26
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: EKCO SRG 601. transformer TR8,9,10 and 11 are audio amp and DC coupled. Attached Thumbnails __________________ Frank

14th Dec 2020, 4:36 pm	#27
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: EKCO SRG 601. transformer The transistors to check and change are TR8, 9, 10 and 11 which are DC coupled. Guide to testing transistors (out of circuit) here:- https://www.vintage-radio.net/forum/...ad.php?t=42194 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

16th Dec 2020, 10:41 am	#28
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer I think I have found the transistors , 3 in copper heat sinks and one small one in the open, i someone could say yay or nay that would be great, whilst I try and buy some of these on eBay. please see pictures attached hopefully they are attached !!

16th Dec 2020, 11:00 am	#29
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: EKCO SRG 601. transformer Yes, remove all 4 transistors from that amp board, note down where they came from and how they were connected. Test them and replace any that show as faulty or suspect. You have the other amp board as a reference should you need it so leave the transistors in that one alone. The red capacitor C81 400uF will need to be changed on both amp boards. That type are known to be unreliable and are probably the original cause for the transformer to burn out. The blue Philips electrolytics are normally OK. What are the smoothing caps like C63, C64, C65, can you show a photo of them? Dont forget to change those 2.2 Ohm resistors you replaced to the proper value of 2.2 ohm. Mike Last edited by crackle; 16th Dec 2020 at 11:13 am.

16th Dec 2020, 11:14 am	#30
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: EKCO SRG 601. transformer I'll just add that the designation 'VT' (Valve Transistor) as in 'VT8' has been used on the PCB rather than the more common 'TR' (Transistor). Be careful in identifying the leads of the new transistors and test them before fitting them. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

23rd Dec 2020, 11:01 pm	#31
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Evening, I have received the transistors i ordered from eBay , but my problem now is practical , even though I can identify each on the circuit diagram , i can't relate that to the real components because only one is identified on the PCB [vt8] thus I am stuck again, any help would be fab, some photos attached thanks yet again Martin Attached Thumbnails

24th Dec 2020, 2:37 pm	#32
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: EKCO SRG 601. transformer The only schematic detail I have is the snippet in Post#13, based on that and the photo's in Post#31: 1st photo.....TR9. 2nd photo.....TR11 on the left and TR10 on the right. 3rd photo.....TR8. The colour coding for the sleeves on TR9, TR10 and TR11: White = Emitter. Green = Base. Red = Collector. So far as I can make out. Lawrence.

30th Dec 2020, 12:35 pm	#33
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Morning hope everyone had a decent Christmas, considering.... I changed and tested the transistors on both RH AND LH boards only one was dud on the RH pcb and one had come loose/unsoldered on the LH pcb. So my next phase is to change those red capacitors which I think are 400uF 18V , but I can't find anyone selling them except Farnell who want £25 quid to deliver a £3 quid part is there anyone else selling these does anyone know ? thanks in anticipation Martin

30th Dec 2020, 1:06 pm	#34
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,876	Re: EKCO SRG 601. transformer Hi You can use 470uF 25V The extra capacitance will be of little consequence and you should be able to find these much cheaper. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

4th Jan 2021, 5:58 pm	#35
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Afternoon all, I have swapped out both red capacitors for 470uF 25V as per. I must have done something wrong , the LH channel was fine. But on the RH channel smoke poured off the insulation of the AC128 transistors , and the transistors are toast. I have ordered some more . But what might I have done wrong ?? I am reluctant to give up . thanks again everyone , Martin

4th Jan 2021, 7:58 pm	#36
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: EKCO SRG 601. transformer Double check the work you have done, perhaps a solder bridge on the print. Of course you could be just unlucky and the transistor whiskers shorted out inside the transistors as they are prone to do. __________________ Frank

13th Jan 2021, 5:18 pm	#37
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer Afternoon, & Eureka!! I am happy to say thanks to everyones help on this forum, I have now got the Ekco radiogram working , both channels ok now, and i have added a separate transformer for the lights. And it looks really good too , I have now to get the record deck to work. But to bring it into this century I want to add a Bluetooth input , so would anyone know where to break into the circuitry to add an audio Input ?? many thanks Martin

18th Jan 2021, 10:52 am	#40
marty-radiogram Triode Join Date: Dec 2020 Location: Wilmslow, Cheshire, UK. Posts: 15	Re: EKCO SRG 601. transformer That's a great tip regarding the Tape Din socket , for Bluetooth. I've dismantled the record deck and basically all the grease has turned to glue, so I've cleaned it all up and re lubricated with new light grease and PTFE oil. It all works well, except when on 33 rpm and auto changer mode ,when the record/LP drops, the turntable nearly stops spinning, its fine on the higher speeds, does anyone know which bit of the mechanism might be causing this ? thanks Martin