Uher CR240 Troubleshooting Best Practice - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

Uncle Bulgaria · 29th Jul 2019, 10:11 am

I'm putting the new switch together now, so it may soon become a 'Success Story'!

Thanks mainly to ms660 - I can't send you a private message Lawrence, so consider a public offer to get you a beer or two. I've really appreciated the time you've taken to deal with my foolish questions on this and the Ferrograph.

ms660 · 29th Jul 2019, 12:11 pm

No worries, schematics can be a bit daunting at times but remember that they can be broken down into individual blocks and those blocks can be broken down into sub circuits that are easier to understand.

If in doubt, always go back to first principles, AC, DC, voltage, resistance, capacitance, inductance, impedance etc. learn the basics of them and they will stand you in good.

My PM isn't enabled anymore, that's because I am unlikely to give or want personal info via it.

I used to give fault finding tips to individuals via PM but don't anymore as I now feel it's better to discuss such things in an open forum for the benefit of other members and future members.

Lawrence.

Uncle Bulgaria · 29th Jul 2019, 12:41 pm

I quite understand. I was only going to offer the aforementioned beer as we're both in Cornwall, and if the sawmilling in your profile is still current I was wondering if you'd be interested in selling any wood. Finding good local timber is a great difficulty!

I'm going away for a month or so, but I will look forward to putting the techniques you've talked me through into practice for the Uher 4000 Report-L that I have stripped down (almost) to its constituent parts...

The switch is in, it works! But is a little too short. Mark II will be longer.

Really chuffed, thank you again.

ms660 · 29th Jul 2019, 1:06 pm

No worries, I don't drink booze anymore, I don't do sawmilling anymore either but I did...a lot.

For fencing timber etc go to a sawmill that does homegrown timber if there's any left, for the better stuff it's the usual builders merchants etc, the only timber I would buy from a DIY shed is small dimension moldings such as beading/doweling etc.

Back when I was in that trade, Truro Sawmills at Penhallow near Truro was the largest homegrown sawmill nearest to where I lived and Cornwall Wood Treatment Services near St. Day was the nearest Tanalizing plant, they also had a good selection of timber both for carcasing and general joinery.

Lawrence.

Uncle Bulgaria · 2nd Aug 2019, 10:01 pm

I'm in Denmark and just plugged the Uher into the boat system via the 12-24V input and T10 caught fire. I thought by removing the lamps until I'm back in the country and can replace them that there'd be no load on T10 as the emitter would be detached from ground. Is that wrong, and by being unloaded and nominally 'on' is T10 drawing current that is overloading it? I'd better take it out of circuit...

ms660 · 3rd Aug 2019, 10:14 am

Probably a short somewhere, check your work.

Lawrence.

Uncle Bulgaria · 3rd Aug 2019, 10:18 am

The irritation is that it was playing well on batteries with nothing altered since.

If T10's OK to be in circuit with no lamps I can look elsewhere for a short, though I'll take it out anyway as it's toast. As I now haven't even got a multimeter to hand more troubleshooting might have to wait!

Frustrating.

Uncle Bulgaria · 21st Oct 2019, 4:04 pm

Back home and trying to put the smoke back in. A labour of love even more as now some of the tracks on the PCB have tried to escape the flames by leaving the board. I've got some Zener diodes on order and have cannibalised a spare board for some transistors.

I think the trouble was that the loudspeaker pressed against a couple of the new capacitors I had put on the main board. As the board was already cracked, this could bring the bottom of the board into contact with the chassis, shorting it. I'm going to insulate the base after replacing the broken components! Fishpaper on the way from RS.

Question:

As some of the new electrolytics are taller than the tantalums they replaced, what is the consensus on ceramic capacitors instead, for the smaller size?

RS has some 100nF, and right up to 470uF MLCC through-hole capacitors! I understand that for some applications they can have the wrong characteristics, but the size is what matters in some positions on these boards, as I discovered to my cost.

29th Jul 2019, 10:11 am	#61
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Uher CR240 Troubleshooting Best Practice I'm putting the new switch together now, so it may soon become a 'Success Story'! Thanks mainly to ms660 - I can't send you a private message Lawrence, so consider a public offer to get you a beer or two. I've really appreciated the time you've taken to deal with my foolish questions on this and the Ferrograph.

29th Jul 2019, 12:11 pm	#62
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Uher CR240 Troubleshooting Best Practice No worries, schematics can be a bit daunting at times but remember that they can be broken down into individual blocks and those blocks can be broken down into sub circuits that are easier to understand. If in doubt, always go back to first principles, AC, DC, voltage, resistance, capacitance, inductance, impedance etc. learn the basics of them and they will stand you in good. My PM isn't enabled anymore, that's because I am unlikely to give or want personal info via it. I used to give fault finding tips to individuals via PM but don't anymore as I now feel it's better to discuss such things in an open forum for the benefit of other members and future members. Lawrence.

29th Jul 2019, 12:41 pm	#63
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Uher CR240 Troubleshooting Best Practice I quite understand. I was only going to offer the aforementioned beer as we're both in Cornwall, and if the sawmilling in your profile is still current I was wondering if you'd be interested in selling any wood. Finding good local timber is a great difficulty! I'm going away for a month or so, but I will look forward to putting the techniques you've talked me through into practice for the Uher 4000 Report-L that I have stripped down (almost) to its constituent parts... The switch is in, it works! But is a little too short. Mark II will be longer. Really chuffed, thank you again.

29th Jul 2019, 1:06 pm	#64
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Uher CR240 Troubleshooting Best Practice No worries, I don't drink booze anymore, I don't do sawmilling anymore either but I did...a lot. For fencing timber etc go to a sawmill that does homegrown timber if there's any left, for the better stuff it's the usual builders merchants etc, the only timber I would buy from a DIY shed is small dimension moldings such as beading/doweling etc. Back when I was in that trade, Truro Sawmills at Penhallow near Truro was the largest homegrown sawmill nearest to where I lived and Cornwall Wood Treatment Services near St. Day was the nearest Tanalizing plant, they also had a good selection of timber both for carcasing and general joinery. Lawrence.

2nd Aug 2019, 10:01 pm	#65
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Uher CR240 Troubleshooting Best Practice I'm in Denmark and just plugged the Uher into the boat system via the 12-24V input and T10 caught fire. I thought by removing the lamps until I'm back in the country and can replace them that there'd be no load on T10 as the emitter would be detached from ground. Is that wrong, and by being unloaded and nominally 'on' is T10 drawing current that is overloading it? I'd better take it out of circuit...

3rd Aug 2019, 10:14 am	#66
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Uher CR240 Troubleshooting Best Practice Probably a short somewhere, check your work. Lawrence.

3rd Aug 2019, 10:18 am	#67
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Uher CR240 Troubleshooting Best Practice The irritation is that it was playing well on batteries with nothing altered since. If T10's OK to be in circuit with no lamps I can look elsewhere for a short, though I'll take it out anyway as it's toast. As I now haven't even got a multimeter to hand more troubleshooting might have to wait! Frustrating.

21st Oct 2019, 4:04 pm	#68
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Uher CR240 Troubleshooting Best Practice Back home and trying to put the smoke back in. A labour of love even more as now some of the tracks on the PCB have tried to escape the flames by leaving the board. I've got some Zener diodes on order and have cannibalised a spare board for some transistors. I think the trouble was that the loudspeaker pressed against a couple of the new capacitors I had put on the main board. As the board was already cracked, this could bring the bottom of the board into contact with the chassis, shorting it. I'm going to insulate the base after replacing the broken components! Fishpaper on the way from RS. Question: As some of the new electrolytics are taller than the tantalums they replaced, what is the consensus on ceramic capacitors instead, for the smaller size? RS has some 100nF, and right up to 470uF MLCC through-hole capacitors! I understand that for some applications they can have the wrong characteristics, but the size is what matters in some positions on these boards, as I discovered to my cost.