Bush TR230 problems - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Hybrid tellies · 3rd Apr 2015, 12:18 am

My TR230 started to sound slightly distorted, very similiar to a rubbing cone speaker defect, a quick check across the PP3 battery showed that it had dropped down to below 6v. Replacing with a good PP9 restored normal clear service.
Having watched/listened to your YouTube video can I suggest a few checks.

First, what is the idle current being drawn from the battery?
Second: again with the volume control at minimum what is the mid point voltage on the output stage?
Finally and if the output stage is ok, tune into a weaker signal or reduce by nulling out one of the stronger signals to see if this reduces or clears the distortion.

To me that distortion sounds more like an AF output fault or possibly an AGC fault and worth checking out before accusing the TAD100 IC.

60 oldjohn · 25th Apr 2015, 11:42 am

I have received the TAD100 from Mike, It was too badly damaged in the post to fit in my set (IC test holder) I was expecting one leg to be missing but there were two missing due to corrosion, others were lost trying to straighten them. The missing pins were 4 and 14. Pin 4 dropped off on removal by OP and pin 14 looks to have been OC or High resistance for a long while, this is under 40x magnification. Pin 14 connects IC to the pcb mounted IF filter block. I hope my diagnosis fits in with the original fault.

John.

Phil G4SPZ · 26th Apr 2015, 10:04 pm

Quote:

Originally Posted by 60 oldjohn

...there were two missing due to corrosion... The missing pins were 4 and 14. Pin 4 dropped off on removal by OP and pin 14 looks to have been OC or High resistance for a long while... I hope my diagnosis fits in with the original fault.

Would the corrosion have been apparent to the OP?

60 oldjohn · 27th Apr 2015, 10:24 am

Just checked and it was only under 60x magnification I could be sure, OP thought the two legs had dropped off on removal, there is a very small bright spot on pin 4 but a blob of corrosion on pin 14. The fault was covered by PCB and only continuity test on each leg would have revealed the fault.
As previously stated I have never known of a faulty TAD100 but if suspected check the legs before condemning the IC.

John.

Phil G4SPZ · 30th Apr 2015, 9:00 pm

Shame that the set's a scrapper, after all the work you've done on it.

3rd Apr 2015, 12:18 am	#41
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,967	Re: Bush TR230 problems My TR230 started to sound slightly distorted, very similiar to a rubbing cone speaker defect, a quick check across the PP3 battery showed that it had dropped down to below 6v. Replacing with a good PP9 restored normal clear service. Having watched/listened to your YouTube video can I suggest a few checks. First, what is the idle current being drawn from the battery? Second: again with the volume control at minimum what is the mid point voltage on the output stage? Finally and if the output stage is ok, tune into a weaker signal or reduce by nulling out one of the stronger signals to see if this reduces or clears the distortion. To me that distortion sounds more like an AF output fault or possibly an AGC fault and worth checking out before accusing the TAD100 IC. __________________ Simon BVWS member

25th Apr 2015, 11:42 am	#42
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Bush TR230 problems I have received the TAD100 from Mike, It was too badly damaged in the post to fit in my set (IC test holder) I was expecting one leg to be missing but there were two missing due to corrosion, others were lost trying to straighten them. The missing pins were 4 and 14. Pin 4 dropped off on removal by OP and pin 14 looks to have been OC or High resistance for a long while, this is under 40x magnification. Pin 14 connects IC to the pcb mounted IF filter block. I hope my diagnosis fits in with the original fault. John. Last edited by 60 oldjohn; 25th Apr 2015 at 11:52 am.

27th Apr 2015, 10:24 am	#44
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Bush TR230 problems Just checked and it was only under 60x magnification I could be sure, OP thought the two legs had dropped off on removal, there is a very small bright spot on pin 4 but a blob of corrosion on pin 14. The fault was covered by PCB and only continuity test on each leg would have revealed the fault. As previously stated I have never known of a faulty TAD100 but if suspected check the legs before condemning the IC. John.

30th Apr 2015, 9:00 pm	#45
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Bush TR230 problems Shame that the set's a scrapper, after all the work you've done on it. __________________ Phil Optimist [n]: One who is not in possession of the full facts