|
Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
|
Thread Tools |
24th Mar 2022, 5:51 pm | #1 |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Bush TR130 inoperative
Whilst trying to restore my Bush TR130 radio, the centre terminal of the headphone socket broke away from its mounting. There is still no sound from the loud speaker. I have checked the transistors, there are no screen to collector s/c in any of the front end transistors. The crystal diode forward resistance is O.K. The OC81D has been replaced by an AC128 by previous restorers. Any suggestions?
There are voltages to the transistors, but no o/p noise heard when touching the centre of the volume control. |
24th Mar 2022, 5:57 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,944
|
Re: Bush TR130 inoperative
Have you tried shorting out the earphone socket?
|
24th Mar 2022, 8:36 pm | #3 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,571
|
Re: Bush TR130 inoperative
Yes try that. If the centre contact has broken away, it will most likely affect the loudspeaker switching. The circuit should show which contact to short out. Alternatively if you don't use headphones or an earpiece you could connect the speaker directly to the output stage, bypassing the headphone socket altogether.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
28th Mar 2022, 1:21 pm | #4 |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Hi. Yes I have tried that method. No sound though. Wonder if the electrolytic coupling & de-coupling caps require replacing? I have tried bridging them but yet no response.
|
29th Mar 2022, 7:09 am | #5 |
Hexode
Join Date: Jun 2012
Location: Chester, Cheshire, UK.
Posts: 421
|
Re: Bush TR130 inoperative
Hi, The electrolytic capacitors used in the Bush TR130 are generally very reliable, that's not to say one or two could be on the way or have failed already but I would lean towards other areas of the circuit first. After bypassing the earpiece socket do you get a pop or other noise through the loudspeaker on switch on? If not then trace the connections to the speaker back through to the output transformer as you might have a high resistance or open circuit here.
Also, a note on the AF117 transistors. Whilst they may not have a direct short from any electrode to the case, it in not uncommon for there to be a leakage path (over and above the normal junction resistance) either between electrodes or from them to case and they can fail in this way at any time. I know there are various methods of clearing any shorts etc but I generally replace then all with a more modern equivalent (AF127 or Russian GT322V for example for reliability. (I know that not everyone does this especially those who prize originality. |
29th Mar 2022, 3:19 pm | #6 |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Hi. Many thanks for the replies. I have discovered that the wire that links the volume control wiper to the circuit board had come away. Re-soldering it in place did restore the background noise, but no stations. The background noise is weak, and you can just hear the buzz from the speaker. Will let you know more as I go on. I do not have any AF127 transistors in stock. Can anyone let me have some, please?
|
29th Mar 2022, 3:48 pm | #7 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,944
|
Re: Bush TR130 inoperative
You don't need to use AF127s. What do you have to hand? Silicon PNP types like BC558s or 2N3906s will probably work. You can always fit Ge types later if you want to.
|
30th Mar 2022, 9:32 am | #8 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
|
Re: Bush TR130 inoperative
You could try gently tapping each AF117 transistor with a pen or small screwdriver handle to se which if any have the tin whisker problem. Have you checked the voltages around the transistors which may give you a clearer picture of the fault.
A faulty detector diode would also cause the same symptoms as you are getting.
__________________
Simon BVWS member |
30th Mar 2022, 10:43 pm | #9 |
Triode
Join Date: Mar 2021
Location: Edinburgh, Scotland, UK.
Posts: 45
|
Re: Bush TR130 inoperative
I had a similar problem with a Bush TR82. It was the detector diode and not the transistors. See my post from about a year ago on this forum.
https://www.vintage-radio.net/forum/...d.php?t=177186 Last edited by Station X; 31st Mar 2022 at 9:04 am. Reason: Link added. |
31st Mar 2022, 11:33 pm | #10 |
Pentode
Join Date: Feb 2015
Location: Belfast, Northern Ireland, UK.
Posts: 130
|
Re: Bush TR130 inoperative
Hi there,
I have just finished the successful repair of a Bush130 and I reckon it is a very fine radio. Initially I suspected the three AF117s and removed them all for testing. Sure enough VT1 and VT2 were dead and, never having had much luck with zapping these troublesome transistors, I replaced both of them, and VT3 as well, with three Russian GT332b transistors kindly provided by another Forum member. Installation was a bit tricky because of the shorter leads and four-square layout of the Russian ones but it's not too bad provided you get the leads bent into a line and each sleeved in different colour. At that point I thought that the job was done but no such luck - I could just about hear a station on MW with the volume full up. I then replaced C30, 8uf coupling capacitor but it was actually fine. However it is connected directly to R16 a 1.5k carbon resistor and that's where the problem was - it had actually split in two across the body. I've never seen that before but when it was replaced I had the great pleasure of listening to all three wavebands including bandspread at full volume and pretty good quality. Have a look at R16 on your PCB, it might just be the same problem lurking. |
1st Apr 2022, 3:08 pm | #11 | |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Quote:
I checked the detector diode and it measured about 380 ohms forward resistance. Should be O.K |
|
1st Apr 2022, 3:11 pm | #12 | |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Quote:
Cheers Mike |
|
2nd Apr 2022, 2:03 pm | #13 |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Hi I found the fault. It wasn't the transistors or the diode detector, and not even resistor R16. It was the electrolytic capacitor C27 (100 uF), which became "leaky". It was pulling the voltage down to 4.5 volts. The supply voltage was 9 volts before the 470 ohm resistor, but after that it was halved.
Cheers Mike |
2nd Apr 2022, 2:10 pm | #14 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,288
|
Re: Bush TR130 inoperative
There's nothing quite like a meter for finding faults!
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
4th Apr 2022, 12:39 pm | #15 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
|
Re: Bush TR130 inoperative
Glad you found the fault. The Bush TR130 are very good radios. Very sensitive and with a powerful output through that large Celestion speaker.
__________________
Simon BVWS member |
5th Apr 2022, 1:52 pm | #16 |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Hi Simon. Many thanks for your reply. The transistor VT1 did "play up" a bit after, and I had to tap it. The pointer is a bit of a nuisance as it came away from its fixing.
|
6th Apr 2022, 12:04 pm | #17 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
|
Re: Bush TR130 inoperative
The pointer or dial drive is a bit fiddly on these radios. I think the circuit diagram or service sheet which you can download from this site should be helpful.
__________________
Simon BVWS member |
11th Apr 2022, 11:49 am | #18 | |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Quote:
Cheers Mike |
|
12th Apr 2022, 9:56 am | #19 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
|
Re: Bush TR130 inoperative
I cant remember the exact layout of the dial drive. Mine has been working fine since I changed the on/off volume control about 15 years ago. Not sure if anyone else can be of help but if not I shall open mine up again,
__________________
Simon BVWS member |
12th Apr 2022, 1:17 pm | #20 | |
Octode
Join Date: Dec 2003
Location: Leeds, West Yorkshire, UK.
Posts: 1,592
|
Re: Bush TR130 inoperative
Quote:
I wonder if the rubber suspension on the tuning gang is causing the carriage to foul the mechanism underneath the cord? Cheers Mike |
|