Bush RP40 No sound - UK Vintage Radio Repair and Restoration Discussion Forum

Kalee21 · 15th Jun 2019, 4:36 pm

I was recently given a Bush RP40 all looks fine and it’s in good condition just one little problem I’ve got no sound inside the valves light up and the power indicator comes on but I get no sound whatsoever it’s as if the speaker is been disconnected which by the way I have tested and it is working and I have also tried a separate speaker and again nothing not a hum a crackle or even a pop i’ve tested the capacitors and resistors and they all seem to be fine except for one which is a mustard colour 10000pf 125v seated under the UCL82 giving no reading are could it be the output transformer do these things go faulty any information will be gladly received

Lucien Nunes · 15th Jun 2019, 5:16 pm

A good first test if there is truly no sound, neither hum or hiss at full volume, would be to check whether there is HT on the reservoir and smoothing capacitors (the two 40uF's.) If that is present, check the DC voltages on the UCL82 pins (other than 4 & 5 which are the heater) all relative to the negative rail. This being a mains-transformer-less 'live chassis' player, everything is connected to the mains including the negative rail, requiring suitable safety precautions when working with the set powered up.

Output transformers do fail, typically the primary winding goes open-circuit. The most likely symptom of that would be no volts on the output valve anode (UCL pin 6). You can test the winding continuity with the set off if you suspect it. This is a hum cancelling transformer so it has a tap near one end where the HT is fed in, and the anode and HT feed to the first stage come from the two ends. You should have a circuit between all 3 leads, and another through the secondary although that hardly ever fails.

Measuring DC voltages at important points such as the HT rail, valve anodes and cathodes can reveal a lot of information quickly about the whole set. Testing individual components is usually better done to confirm a diagnosis, or to decide whether to replace aged components in an otherwise working circuit. However, if you do not have an isolating transformer or you are concerned about working with the set powered up, then 'dead' tests such as transformer continuity are undoubtedly a safer way to check for certain common problems.

Stylo N M · 15th Jun 2019, 9:49 pm

Hi,

just a suggestion, check to see if you have an open circuit speech coil.

Paul

John10b · 16th Jun 2019, 10:39 am

In post #1 he said he has tested speaker and tried another one.
Cheers
John

Stylo N M · 16th Jun 2019, 11:44 am

Apologies i did read through the first post, but
somehow genuinly managed to miss that bit john my mistake

Paul

vinrads · 16th Jun 2019, 2:58 pm

It sounds like you have a multi meter, can you check if you have HT on the smoothing capacitor DC range, guess you should have 200VDC plus. Mick.

Kalee21 · 18th Jun 2019, 1:09 pm

Just an update on the issue with the bush amplifier having tested all the components it now looks like the output transformer is the fault I borrowed a friends Dansette Capri which is basically the same amplifier minus the bass
(See photo of Capri transformer)I found that the two outer pins on the amplifier side of the Capri gave a reading of 533.6ohm but on the RP40 nothing testing all the other pins they gave a rough reading of that of the Capri
I think I’ll put it in storage and keep my eye open for a suitable replacement hopefully

15th Jun 2019, 5:16 pm	#2
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Bush RP40 No sound A good first test if there is truly no sound, neither hum or hiss at full volume, would be to check whether there is HT on the reservoir and smoothing capacitors (the two 40uF's.) If that is present, check the DC voltages on the UCL82 pins (other than 4 & 5 which are the heater) all relative to the negative rail. This being a mains-transformer-less 'live chassis' player, everything is connected to the mains including the negative rail, requiring suitable safety precautions when working with the set powered up. Output transformers do fail, typically the primary winding goes open-circuit. The most likely symptom of that would be no volts on the output valve anode (UCL pin 6). You can test the winding continuity with the set off if you suspect it. This is a hum cancelling transformer so it has a tap near one end where the HT is fed in, and the anode and HT feed to the first stage come from the two ends. You should have a circuit between all 3 leads, and another through the secondary although that hardly ever fails. Measuring DC voltages at important points such as the HT rail, valve anodes and cathodes can reveal a lot of information quickly about the whole set. Testing individual components is usually better done to confirm a diagnosis, or to decide whether to replace aged components in an otherwise working circuit. However, if you do not have an isolating transformer or you are concerned about working with the set powered up, then 'dead' tests such as transformer continuity are undoubtedly a safer way to check for certain common problems.

15th Jun 2019, 9:49 pm	#3
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Bush RP40 No sound Hi, just a suggestion, check to see if you have an open circuit speech coil. Paul

16th Jun 2019, 10:39 am	#4
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,882	Re: Bush RP40 No sound In post #1 he said he has tested speaker and tried another one. Cheers John

16th Jun 2019, 11:44 am	#5
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Bush RP40 No sound Apologies i did read through the first post, but somehow genuinly managed to miss that bit john my mistake Paul

16th Jun 2019, 2:58 pm	#6
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,755	Re: Bush RP40 No sound It sounds like you have a multi meter, can you check if you have HT on the smoothing capacitor DC range, guess you should have 200VDC plus. Mick.

15th Jun 2019, 4:36 pm	#1
Kalee21 Triode Join Date: Nov 2018 Location: Manchester, UK. Posts: 40	Bush RP40 No sound I was recently given a Bush RP40 all looks fine and it’s in good condition just one little problem I’ve got no sound inside the valves light up and the power indicator comes on but I get no sound whatsoever it’s as if the speaker is been disconnected which by the way I have tested and it is working and I have also tried a separate speaker and again nothing not a hum a crackle or even a pop i’ve tested the capacitors and resistors and they all seem to be fine except for one which is a mustard colour 10000pf 125v seated under the UCL82 giving no reading are could it be the output transformer do these things go faulty any information will be gladly received

18th Jun 2019, 1:09 pm	#7
Kalee21 Triode Join Date: Nov 2018 Location: Manchester, UK. Posts: 40	Re: Bush RP40 No sound Just an update on the issue with the bush amplifier having tested all the components it now looks like the output transformer is the fault I borrowed a friends Dansette Capri which is basically the same amplifier minus the bass (See photo of Capri transformer)I found that the two outer pins on the amplifier side of the Capri gave a reading of 533.6ohm but on the RP40 nothing testing all the other pins they gave a rough reading of that of the Capri I think I’ll put it in storage and keep my eye open for a suitable replacement hopefully Attached Thumbnails