20th Nov 2017, 9:41 pm | #21 |
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Re: Bush AC 11
Colours are orange,white,orange, silver
measures 47k bill |
20th Nov 2017, 11:41 pm | #22 |
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Re: Bush AC 11
Black = 0,
Brown = 1, Red = 2, Orange = 3, Yellow = 4, Green = 5, Blue =6, Purple =7, Grey = 8, White = 9 First band is first digit, Second band is second digit, Third band is number of zeros. fourth band is tolerance none=20%, silver is 10%, gold is 5%. So your resistor is 39000 Ohms, 39k Ohms, 10%. So it is out of tolerance |
21st Nov 2017, 3:42 pm | #23 |
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Re: Bush AC 11
Pin 1 h
Pin 2 a-hex 120V Pin 3 a-t 60V measured 0,1V Pin 4 g-t Pin 5 screen-hex 60V measured 81V Pin 6 g-hex Pin 7 k 1.2V measured 1.3V Pin 8 h R3 k 220 R4 g-t 47k The triode grid is referred to the cathode via R4 and should be negative with respect to to the cathode. The triode anode is fed through a coil depending on the band chosen and should be similar to pin 5 screen-hex. There is an obvious fault here, find the break, it could be in the wavechange switch or the coil. * Trader numbers. |
21st Nov 2017, 5:33 pm | #24 |
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Re: Bush AC 11
If pin 3 of the UCH42 has not got around 81v on any of the wavebands and yet the screen has 81v, then its either all the switch contacts S19,S20,S21 or all the coils L11,L12,L13 are open circuit, very improbable.
I suspect the wiring may have been got at, especially as the extra resistor seems to be connected to this valve holder. You will have to check the circuit through with a meter from R2 (15k ohms, brown, green, orange ) to the anode pin3 on each waveband. |
21st Nov 2017, 7:38 pm | #25 |
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Re: Bush AC 11
There appears to be a missing wire...screen grid to osc coils.
Photo here showing where the missing link wire is connected to from the screen grid to osc coils: https://www.vintage-radio.net/forum/...4&d=1501362155 It still doesn't account for the 39k resistor feed from HT to the osc anode though, if that's where it was connected to, two possibilities I can think of are...an attempt to tame an osc that has birdies or a mod to convert from series fed feedback to shunt fed feedback for whatever reason, if it was the latter I would expect to see an extra capacitor somewhere as a DC blocker. Just thinkin' Lawrence. Last edited by ms660; 21st Nov 2017 at 7:48 pm. Reason: correction |
21st Nov 2017, 7:54 pm | #26 |
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Re: Bush AC 11
Hi Lads,
no luck so far in locating break in supply but while doing that came across additional wire connecting coil and wave changer. This wire is not present in another working AC 11 I completed some time ago. Picture attached Thanks Bill |
21st Nov 2017, 8:38 pm | #27 |
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Re: Bush AC 11
Yes Lawrence you are right ....there is a wire missing from pin 5 to coil
see photos thanks Bill |
21st Nov 2017, 9:33 pm | #28 |
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Re: Bush AC 11
It's a bit of a mess, if you look at the wave band switch where that extra wire from the osc coil assembly is connected it appears to connect to the PU side of S22 which in turn connects to the PU socket itself if I'm looking at things right.....See here:
http://www.vintage-radio.net/forum/a...6&d=1156968882 I would be looking at putting things back as per the schematic...very slowly...then take things from there. Lawrence. |
21st Nov 2017, 11:03 pm | #29 |
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Re: Bush AC 11
Yes,thanks for that ...I will start putting things back again tomorrow
Bill |
22nd Nov 2017, 12:56 pm | #30 | |
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Re: Bush AC 11
Quote:
Lawrence. |
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22nd Nov 2017, 5:50 pm | #31 |
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Re: Bush AC 11
Hi Lads,
I have replaced the "missing wire on pin 3 V1 and removed the additional wire connecting the coil to wave changer. I have the following voltages on V1 Pin 2 109.0 Pin 3 57.0 Pin 5 57.0 Pin 7 1.3 I can now tune in RTE LW, BBC LW but the volume is extremely low. Almost inaudible unless I put my ear to the speaker. Some MW but unable to clarify. I had already cleaned the volume control switch but will look at this again, any other possibilities??.....Making progress! thanks Bill |
22nd Nov 2017, 7:01 pm | #32 |
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Re: Bush AC 11
Check how it performs on "gram" with an input from MP3 or CD or record etc. If the volume then is reasonable you can reckon that the audio stages V3 and V4 are working reasonably.
Check C29 (trader sheet) carefully for leakage before running it for too long, there should be less than a volt on the grid of the output valve, pin 6 of V4 else you risk your output transformer. If in doubt, replace it. |
23rd Nov 2017, 12:57 am | #33 |
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Re: Bush AC 11
You still have not measured the voltage of the V1 triode grid (pin4).
This should be a few volts negative. If the oscillation level is low, the sensitivity could be low. A more likely cause is that the phantom fiddler has twiddled the IF transformer cores and the set is well out of tune. You will need a signal generator and counter to re-align but the cores may be seized and can easily be broken. |
23rd Nov 2017, 4:44 pm | #34 |
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Re: Bush AC 11
Pin 4 V1 is measuring -6.3
Pin 6 V4 is measuring .02v Checking Volume switch again Thanks Bill |
23rd Nov 2017, 5:04 pm | #35 |
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Re: Bush AC 11
Oscillator is running OK. Coupling cap seems good too, unusually.
Check the audio output as my last post to determine whether the volume is low due to the IF being down or the audio stages. Otherwise you will be chasing your tail. Only attempt re-alignment if it has been "twiddled" as its a risk you may not need to take. The adjusters were sealed with a white compound in the factory, if its still there the alignment should still be correct. The IF cores can break but the ones in the side of the cans with lock nuts are better than the ones in top and bottom. Slacken the nuts before trying to move them to correct the alignment if you find you must re-align the set. |
24th Nov 2017, 6:43 pm | #36 |
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Re: Bush AC 11
Hi Lads,
Removed volume control, dismantled and cleaned again,refitted and low and behold, full volume, tone excellent, no crackles. Now tuning a wide range of stations on LW/MW Entirely possible one of the solder joints was not up to scratch after my initial cleaning of the volume control. Happy now and thanks to all for contributions and pointers. I will post a pic when fully re-assembled Bill |
26th Nov 2017, 12:46 pm | #37 |
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Re: Bush AC 11
Hi Lads,
Photos of radio. There are a few scratches and marks reflecting it's age. I considered sanding down the complete cabinet and re-varnishing but decided against that as I wanted it to look original. I did remove both grills and cleaned and repainted them. other than that plenty of wax and polishing Thanks again for all your help Bill |