Grundig Party Boy 700 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Sideband · 5th Mar 2024, 8:52 pm

C71 on your picture looks like a tantalum electrolytic. If that's the case there is a spot on one side and with the spot facing you, the + lead is on the right. It's just the way tantalum caps are marked.

pepmin 1 · 6th Mar 2024, 1:47 am

Hi. Thanks for that. I did wonder if that was what it meant. Colin

pepmin 1 · 9th Mar 2024, 10:15 pm

Hi. Just thought I would pick your brains one last time about this radio. I have changed the electrolytics, checked all off the resistors and checked the transistors. To my eyes everything as far as that goes seems to be okay. I removed the two Zener diodes and checked that the power goes one way only and that that seems okay. I realize that there are that more in depth ways of checking but that is as far as I can go. I still have the same fault in that the BC639 output transistor gets very hot. I have a transistor shape on my finger to prove it. I changed the transistor out for a new one and that got very hot and has failed. I haven't checked any of the non polarized capacitors yet is that a possibility? I also have not removed the cover marked with the red dot in the pic. I know there are resistors and a transistor under there but the cover is well soldered to the board so I have left alone for now, In the few seconds that the transistor takes to get hot the crackle in the speaker is louder but still only a crackle. Is there any worth while checks I can do with the output transistor out of circuit as it only takes seconds to get extremely hot. Thx Colin.

5th Mar 2024, 8:52 pm	#21
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,585	Re: Grundig Party Boy 700 C71 on your picture looks like a tantalum electrolytic. If that's the case there is a spot on one side and with the spot facing you, the + lead is on the right. It's just the way tantalum caps are marked. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

6th Mar 2024, 1:47 am	#22
pepmin 1 Pentode Join Date: Nov 2010 Location: Inverness, Scottish Highlands, UK. Posts: 226	Re: Grundig Party Boy 700 Hi. Thanks for that. I did wonder if that was what it meant. Colin

9th Mar 2024, 10:15 pm	#23
pepmin 1 Pentode Join Date: Nov 2010 Location: Inverness, Scottish Highlands, UK. Posts: 226	Re: Grundig Party Boy 700 Hi. Just thought I would pick your brains one last time about this radio. I have changed the electrolytics, checked all off the resistors and checked the transistors. To my eyes everything as far as that goes seems to be okay. I removed the two Zener diodes and checked that the power goes one way only and that that seems okay. I realize that there are that more in depth ways of checking but that is as far as I can go. I still have the same fault in that the BC639 output transistor gets very hot. I have a transistor shape on my finger to prove it. I changed the transistor out for a new one and that got very hot and has failed. I haven't checked any of the non polarized capacitors yet is that a possibility? I also have not removed the cover marked with the red dot in the pic. I know there are resistors and a transistor under there but the cover is well soldered to the board so I have left alone for now, In the few seconds that the transistor takes to get hot the crackle in the speaker is louder but still only a crackle. Is there any worth while checks I can do with the output transistor out of circuit as it only takes seconds to get extremely hot. Thx Colin. Attached Thumbnails