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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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11th Mar 2016, 1:27 pm | #61 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Looking like it won't be a good weekend after all...
Having powered up slowly three or four times with the variac yesterday, I put on the three pin plug and connected up directly to the mains today. After less than a minute I had smoke coming from the base of the UM4. In an earlier post I mentioned that the nominal 100 ohm res between pins 2 and 7 of the UM4 read around 370 ohms and I decided to connect another res in parallel to take it down to about 100 ohms. To gain some wattage I used a parallel combination of four larger resistors instead of a single one - the final res value I had was 97 ohms. Those resistors were the source of the smoke but I had the same 97 Ohm res value afterwards. I went back to the variac and brought it back up slowly and at about 210 V the smoke problem recurred. The UM4 did light up however, so that aspect seems to be basically OK. I then removed the four new res and found the old res reading was 256 ohm. The only other change I had made from yesterday was to connect some wire into the aerial. In the process of picking up and laying down different pieces of wire to use as an aerial I may have caused the problem - I had accidentally left a piece of cable (with the ends of the leads exposed) over the back of the speaker and it may be that I shorted the two leads to the speaker but I'm not sure. The speaker still works OK and there's the same background sound as there was yesterday. I'm hoping there's a way out of this difficulty - as ever, eager to hear your opinions. |
11th Mar 2016, 2:13 pm | #62 |
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Join Date: Jun 2003
Location: Oxford, UK
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Re: Bush BS35 (Ireland) - new restoration
Shorting the speaker won't have done any harm.
I don't really understand what you've done around the UM4 base, but it sounds as if you may have introduced a short circuit. |
11th Mar 2016, 6:13 pm | #63 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Bush BS35 (Ireland) - new restoration
I should leave the extra resistors off, don't worry too much about finessing the magic eye circuitry until you're happy about the functioning of the rest of the set. Magic eye wiring frequently involves a bundle of flying wires feeding a slightly flimsy Paxolin or similar valveholder with various components and wire links mounted around the holder. It's possible that the series heater chain was being partially shorted by the 100ohm resistor mentioned earlier touching one side and feeding it to chassis- it's conceivable that this is what would have caused it to go high in value originally through overheating and that when the parallel resistors were added this increased the severity of the diverted current, hence the smoke. Check the wiring and linking around the magic eye socket carefully to see that no bare leads or contacts have been disturbed and bent against each other- this is the sort of fault that may have been latent since new, just waiting for a slight movement of the wire bundle.
Sometimes folk (me included) who are used to parallel heater chains with relatively low and innocuous voltages can be taken aback by the voltages present in series chains- but manufacturers still strung them around willy-nilly without sleeving or covers and the clearance between valve-socket contacts can be rather minimal. A 100ohm resistor diverting some current to chassis might not have robbed the heater chain sufficiently to stop the set working- but it could get hot and bothered itself. Don't worry too much about a possible brief short across the loudspeaker terminals- valves are generally robust to this, it's an open circuit that is problematic, as without the loading of a speaker very high peak voltages can occur on the primary side which may harm the output transformer or valve. |
11th Mar 2016, 9:25 pm | #64 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Thanks for posts.
I wonder if the UM4 problem is one that was there before when it was previously 'repaired'. In an earlier post I mentioned that one wire to the UM4 had been left disconnected - it was deliberately disconnected, folded back carefully away from the base, and perhaps the guy doing the repair took that course of action to eliminate the short circuit current. In any case, I'll check everything carefully around the UM4 base. I wondered also if it could be the case that the short occurs up only when the UM4 is warmed up? I'll be away from the radio for the weekend unfortunately - back to the bench on Monday. |
11th Mar 2016, 11:07 pm | #65 |
Hexode
Join Date: Sep 2013
Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland.
Posts: 499
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Re: Bush BS35 (Ireland) - new restoration
Just an observation from working on my BS35. A lot of the rubber insulated wiring was crumbling - maybe carefully check for any shorts in the loom going to the UM4.
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Dom Less snakes...more ladders! Last edited by sexton_mallard; 11th Mar 2016 at 11:12 pm. |
12th Mar 2016, 6:44 pm | #66 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
The same story about the UM4 wiring loom applied in my case also. The two heater wires were OK but the insulation on all the others had crumbled so I replaced them. The base contacts are very loose and floppy (mentioned above by Turretslug) so I will check in case there's a contact between them somewhere.
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14th Mar 2016, 3:56 pm | #67 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Did a thorough check around the UM4 base and found nothing the matter there. Did find that one solder joint I had made on the board had come away so I re-did that and checked that all the others were OK. Powered up again using variac with UM4 in place - got radio reception for a while but then noticed problem at UM4 base again when supply was at about 210V for 5 mins or so. Decided to take out UM4 (removed all leads except for heater) and powered up slowly (over about 25 mins) again using variac. Radio reception was fine again (first sounds at about 150 V) but decided to not go above 200 V. Left it running for 15 mins and it was steady all the time. Had to quit at that stage.
There were some cracks and pops in my first session today with the power supply at 210 V and I wonder if there could be a problem that kicks in at those voltages. Also, it seems that the UM4 may have a problem. Regarding the sound quality, there's a bit of low frequency distortion and a noticeable general background noise. Will try using aerial next session (tomorrow). Great to get back to hearing the radio again, and thanks for your help. |
14th Mar 2016, 4:03 pm | #68 |
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Join Date: Jun 2003
Location: Oxford, UK
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Re: Bush BS35 (Ireland) - new restoration
You can't expect the radio to function well if you are running it way below the correct voltage. If you are pretty confident that you have eliminated the UM4 problem, at least temporarily, then wind it up to 230V and see what happens.
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15th Mar 2016, 7:13 pm | #69 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Update on Bush BS35 operation
Resumed checking with UM4 disconnected (excluding series heater). Connected directly to the mains today and got stable operation for two hours on the one station (RTE longwave) that I am receiving without an aerial. Some background noise and some distortion of base frequencies present as noted before. I found the following voltages on the valve pins. I don’t know the function of all the individual valves but hopefully you will know if the voltages are typical for the valve. Heater voltages on two pins (1 and 8): UY41 142V and 110V UL41 110V and 66V First UF41 66V and 55V Second UF41 55V and 44V UM4 44V and 30V UCH42 30V and 17V UBC41 17V and 4V Also got the following: UY41 has 230V AC on pin 2 and 198V DC on pin 7 UL41 has 185V DC on pin 2 and 100V DC on pin 5 First UF41 has 63V DC on pin 2 and 65V DC on pin 5. Contacting pin 6 cancels sound. Second UF41 has 81V DC on pin 2 and 72V DC on pin 5. Contacting pin 6 increased sound. UM4 not connected (except heater) but lead to pin 4 has 198V DC UCH42 has 82V DC on pin 3 and 65 V DC on pin 5. Contacting pin 2 cancels sound UBC41 has 70V DC on pin 2. Contacting pins 5 and 6 cancels sound. If these values are typical then I will reassemble the radio. The two lights for the station display are both OK (both 2.2 ohms). Thanks for all comments and assistance to date |
15th Mar 2016, 9:16 pm | #70 |
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Re: Bush BS35 (Ireland) - new restoration
Without checking the service data, all these numbers look plausible.
There is no point in running this radio without any aerial at all. Some radios of this era had frame or ferrite rod aerials which allowed them to give good reception without an external aerial, but this isn't one of them. Even a couple of yards of wire connected to the aerial socket will transform things. No offence meant, but I think you are possibly the most cautious repairer/restorer we've ever had on the forum |
16th Mar 2016, 12:25 am | #71 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
A fair comment. Smoke coming from the base of a valve made me even more cautious than I already was! I'm not actually hesitating to use an aerial, I just carried on with checking the voltage readings without an aerial in place.
The radio in question is particularly important to me as it was the first bought in the family 60 odd years ago. I rescued it from being dumped, and if I am to destroy a radio by accident I don't want it to be this one. So, novice that I am, caution is the name of the game for this radio. Thanks for staying with the story! |
16th Mar 2016, 10:06 pm | #72 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Put the radio back together today and added an aerial. Very happy with the outcomes - good reception for several stations on all bands. There are several British stations on medium wave, and what sounds like lots of Indian stations on shortwave. There's a mechanical glitch or two to be ironed out - the tuning cord runs over the metal fixtures that hold the pointers at a couple of places and the pointers are misplaced a little from the correct wavelengths.
I still have to finish off the cabinet, find a UM4, an On/Volume knob, and a new back cover, but overall I'm delighted to have the old family radio back in action - thanks very much for all your advice and information and considerable patience. I think I have attached a pic! |
17th Mar 2016, 1:03 am | #73 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Bush BS35 (Ireland) - new restoration
Very satisfying once something's up, running and proven. Nice-looking, understated set, too.
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28th Jul 2016, 2:06 pm | #74 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
After enjoying using the radio for several months of occasional use (it's in a holiday home) a glitch has occurred with the tuning of the BS35. I normally have it on for short periods of at most an hour, but one day when I had it running for a longer time I found that it had de-tuned such that I got the 252 kHz RTE1 signal at about 230 kHz. However, I cannot say whether the original or the new setting is the correct one as I used the 252 kHz signal to position the pointers (about 1190 m on LW)! It seemed to be about right as the tuning capacitor and pointers were both fairly close to one end of their adjustment ranges and the pointers covered the full range when the tuning knob was turned over the full range. The problem has recurred again on two occasions but I haven't yet 'caught it in the act' so I can't say whether it is a sudden or gradual de-tuning (next time I'll sit and listen). Meanwhile, I would welcome comments on this sort of problem and likely causes.
Thanks again for help along the way |
28th Jul 2016, 2:19 pm | #75 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
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Re: Bush BS35 (Ireland) - new restoration
Is it just LW that's moving or does MW drift aswell?
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28th Jul 2016, 2:25 pm | #76 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
I didn't check any other bands or stations - I will do so at the weekend.
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5th Aug 2016, 11:33 pm | #77 |
Triode
Join Date: Oct 2015
Location: Dublin, Ireland
Posts: 42
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Re: Bush BS35 (Ireland) - new restoration
Further to query from Nuvistor - I checked the medium band and found BBC5 at approx 310 m and 415 m. Correct wavelengths are 330 and 432 m I believe. I heard another British station at approx 1620 m on LW. On VHF3 I found an American station at 6.2 MHz and another? American station on VHF2 at 10 MHz.
The setting for RTE is now steady at approx 1275 m, i.e. it no longer jumps frequency after being turned on. |
6th Aug 2016, 12:24 am | #78 |
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Re: Bush BS35 (Ireland) - new restoration
BBC R4 LW on 198KHz should tune in at about 1515 metres. RTE R1 and BBC R4 are the only English language stations on LW.
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