Hacker Sovereign output transistor problem - UK Vintage Radio Repair and Restoration Discussion Forum

fordboy · 12th Jul 2009, 4:11 pm

I'm restoring a Hacker Sovereign in blue and I have had a few problems. The set works but after a few miniutes of being on the set gets gradually quieter. At the same time the battery voltage gets lower. After a while both transistors were smoking, and were hot to the touch. I unsoldered one and I've tested it and it has a HFE of 1. What this means I don't know

What I would like to know is if the transistor is at fault or something else. I checked the caps for short circuits in the circuit and didn't see anything.

I'm fairly new to all this electronics lark but I'm restoring it to go with my mate's classic car. Any help would be greatly appreciated

Cheers,

Liam

Steve_P · 12th Jul 2009, 4:26 pm

An HFE of 1 suggests that that transistor is knackered.

Remove them both and bin them. Check the conditions without them in and then replace TR4, TR5 and TR6. Then power it up and see if it still overheats. If it does, come back.

Cheers,

Steve P.

fordboy · 12th Jul 2009, 5:08 pm

Thanks I'll have a look

fordboy · 26th Jul 2009, 2:52 pm

ok replaced both output transistors, switched on and all is well apart from the fact the transsitors were red hot and smoking
im guessing a resistor in the biasing part of the circuit has gone low?
can anyone please tell me the voltages i should expect to see in the circuit?
thankyou for all your help

fordboy · 26th Jul 2009, 6:58 pm

update:
Ive found that r14 is overheating aswell so do we think that this is the problem or merely a symptom of the problem?
cheers

Liam

Steve_P · 26th Jul 2009, 9:06 pm

There are several Hacker sets that call themselves Sovereign. Is there a type or model no. anywhere at all? If not, a picture may help?

I think it's the RP18. Anyway, once you know, the manual is up top there. Check for faulty tracks, bad soldered joints and solder bridges.

Change the Electrolytic caps - on the RP18 it's C7, C9, C10, C11 and C13. May be leaky. And check RV4 - the rough check is to adjust for 9v (supply is 18 Volts) on C23. Might be worth changing this one too.

Cheers,

Steve P.

fordboy · 30th Jul 2009, 6:29 pm

Its a hacker sovereign rp25B and ill get the circuit diagram and check it out.

cheers,

Liam

12th Jul 2009, 4:11 pm	#1
fordboy Triode Join Date: Jul 2009 Location: Slough, Berkshire, UK. Posts: 10	Hacker Sovereign output transistor problem I'm restoring a Hacker Sovereign in blue and I have had a few problems. The set works but after a few miniutes of being on the set gets gradually quieter. At the same time the battery voltage gets lower. After a while both transistors were smoking, and were hot to the touch. I unsoldered one and I've tested it and it has a HFE of 1. What this means I don't know What I would like to know is if the transistor is at fault or something else. I checked the caps for short circuits in the circuit and didn't see anything. I'm fairly new to all this electronics lark but I'm restoring it to go with my mate's classic car. Any help would be greatly appreciated Cheers, Liam Last edited by Station X; 12th Jul 2009 at 4:19 pm.

12th Jul 2009, 4:26 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: hacker sovereign output transistor problem An HFE of 1 suggests that that transistor is knackered. Remove them both and bin them. Check the conditions without them in and then replace TR4, TR5 and TR6. Then power it up and see if it still overheats. If it does, come back. 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...?

12th Jul 2009, 5:08 pm	#3
fordboy Triode Join Date: Jul 2009 Location: Slough, Berkshire, UK. Posts: 10	Re: hacker sovereign output transistor problem Thanks I'll have a look Last edited by Brian R Pateman; 12th Jul 2009 at 5:15 pm. Reason: Quote of preceding post removed.

26th Jul 2009, 2:52 pm	#4
fordboy Triode Join Date: Jul 2009 Location: Slough, Berkshire, UK. Posts: 10	Re: Hacker Sovereign output transistor problem ok replaced both output transistors, switched on and all is well apart from the fact the transsitors were red hot and smoking im guessing a resistor in the biasing part of the circuit has gone low? can anyone please tell me the voltages i should expect to see in the circuit? thankyou for all your help

26th Jul 2009, 6:58 pm	#5
fordboy Triode Join Date: Jul 2009 Location: Slough, Berkshire, UK. Posts: 10	Re: Hacker Sovereign output transistor problem update: Ive found that r14 is overheating aswell so do we think that this is the problem or merely a symptom of the problem? cheers Liam

26th Jul 2009, 9:06 pm	#6
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Hacker Sovereign output transistor problem There are several Hacker sets that call themselves Sovereign. Is there a type or model no. anywhere at all? If not, a picture may help? I think it's the RP18. Anyway, once you know, the manual is up top there. Check for faulty tracks, bad soldered joints and solder bridges. Change the Electrolytic caps - on the RP18 it's C7, C9, C10, C11 and C13. May be leaky. And check RV4 - the rough check is to adjust for 9v (supply is 18 Volts) on C23. Might be worth changing this one too. 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...?

30th Jul 2009, 6:29 pm	#7
fordboy Triode Join Date: Jul 2009 Location: Slough, Berkshire, UK. Posts: 10	Re: Hacker Sovereign output transistor problem Its a hacker sovereign rp25B and ill get the circuit diagram and check it out. cheers, Liam