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Old 25th Jan 2012, 12:06 am   #161
PJL
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Default Re: Bush AC34, no sound.

Wahooo!!!! You must be pleased to hear something from it.

The circuit is a bit different from the AC34 and the oscillator anode feed is on a tag strip by the tuning flywheel connected by red wires. It looks like blue grey red? Can you check it's value.

Can you tune to a station and flick the wavechange a bit to see if it improves or changes.

Can you measure the voltages on the UF41 (IF) that is furthest from the wavechage switch so we can see what changes the swap has made.

I see there are still a couple of wax capacitors around that may need to be changed.

It's also worth cleaning valve pins and sockets with Servisol. Don't get it on the print as it will wipe right off.

Lastly, you might want to try chaging the UF41's out with the original ones from the set.
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Old 25th Jan 2012, 10:57 am   #162
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Default Re: Bush AC34, no sound.

As PJL says, change the remaining waxies. A check on all resistor values and replacement of any more than 20% off spec would be a good idea too.
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Old 25th Jan 2012, 8:47 pm   #163
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Default Re: Bush AC34, no sound.

Thanks lads,
Yes delighted......could not believe my ears after all the trying and checking.
I will work away on your tips and I have some resistors ordered to replace those out of spec, I have the caps to replace the waxies and I will report back. Have to earn a crust over the next couple of days,so please be patient and I will be back ASAP.
Thanks
Bill
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Old 27th Jan 2012, 8:39 pm   #164
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Default Re: Bush AC34, no sound.

Hi lads
Just a question please,
I got some new resistors today, they are tiny in comparison to the old ones in the radio. Measurements and colour codes are the same. Are they ok to use?
Thanks
Bill
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Old 27th Jan 2012, 9:46 pm   #165
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Default Re: Bush AC34, no sound.

These are most likely 1/4 watt resistors. They are fine for most of your set, but there are a couple of 1/2 watt and a 2-watt in the AC34. These ones may not need to be changed. If you have a problem with the resistors, PM me and I can send you some of the correct wattage.

Gus.

Edited to add - if the old ones measure okay, just leave them.

Last edited by westcliff; 27th Jan 2012 at 9:47 pm. Reason: Addition
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Old 28th Jan 2012, 9:41 pm   #166
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Default Re: Bush AC34, no sound.

Thanks Gus
I will do that shortly
Bill
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Old 1st Feb 2012, 10:04 pm   #167
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Default Re: Bush AC34, no sound.

Hi all,
did some work over the last few days, replaced last of the wax capacitors, checked the resistors and found all within 20% of spec except 1, sorry don't know the number but it is beside the big rod resistor on the tag board, (yellow,purple,yellow) measured 665k ohms. I have not replaced it yet.
Cleaned as much as possible,blew out any dust/debris and replaced some damaged wires.
I can just about get some short wave transmissions, nothing on med. or long wave. Lots of noise and crackle when turning the tuning knob especially at the top end of the tuning fins. Exasperation beginning to set in....
I have taken the liberty of posting the valve voltages again ,perhaps something might show up.

UY41
pin 1 brown 158.5 ac (Heater)
pin 2 red 253.9 ac (Anode)
pin 3,4,5,6 blank
pin 7 red 287.7 dc (Cathode)
pin 8 brown 127.3 ac (Heater)

UL41
pin 1 brown 126.7 ac (Heater)
pin 2 blue 273.6 dc (Anode)
pin 3 blank
pin 4 green 1.07 dc
pin 5 red 119.4 dc (Screen Grid)
pin 6 resistor between this pin and pin 4,(yellow,violet,orange 53.4K) (Grid)
pin 7 yellow 8.9 dc (Cathode)
pin 8 brown 79.0 ac (Heater)

UBC41
pin 1 brown 9.17 ac (Heater)
pin 2 blue 77.2 dc (Anode)
pin 3 to volume control (Control Grid)
pin 4 to earth and centre of valve, also resistor to pin 6,( brown,black,green 1.07M)
pin 5 to can l16? (D2)
pin 6 green 2.9ac (D1)
pin 7 yellow 1.24 dc (Cathode)
pin 8 brown23.3 ac (Heater)

UF41
pin 1 brown 77.8 ac (Heater)
pin 2 orange 79.3 dc (Anode)
pin 3,4 blank
pin 5 purple 55.5 dc (Screen Grid)
pin 6 resistor (red,red,brown 224 ohms) (Control Grid)
pin 7 yellow 1.51dc (Cathode)
pin 8 brown 35.4 ac (Heater)

UF41
pin 1 brown 50.6 ac (Heater)
pin 2 blue 71.3 dc (Anode)
pin 3,4 blank
pin 5 purple 56.8 dc (Screen Grid)
pin 6 green 0.16 ac (Control Grid)
pin 7 yellow 1.11 dc (Cathode)
pin 8 brown 63.7 ac (Heater)

UCH42
pin 1 brown 22.9 ac (Heater)
pin 2 blue 114 1 dc (Anode)
pin 3 green 2.6 ac (Anode of triode)
pin 4 resistor to pin 7 (yellow,violet,orange,50K) (Grid of triode)
pin 5 purple 80.5 dc (Grid 2 and Grid 4, Screen)
pin 6 green 0.1 ac (Grid 1)
pin 7 yellow 1.55 dc + capacitor 50nf (Cathode)
pin8 brown 37.3 ac (Heater)

One thing I noticed when i powered up, the first 2 valves UY41 and UL 41 lit up very quickly almost like a camera flash and subsided to a glow.
thanks to all for your help, it's a difficult one
bill

M
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Old 1st Feb 2012, 10:22 pm   #168
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Default Re: Bush AC34, no sound.

Look at the readings for pins 1 & 8 (brown wires) on the two UF41s. for each valve subtract the lower voltage reading from the higher voltage reading to give the heater voltage.

You'll find that one valve is running at 12.6V which is OK and the other at 42.4 volts, which is not OK.

Recheck the readings. Check that the valves are seated correctly. Check that both valves are UF41s. Try swapping them over and rechecking the readings.
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Old 1st Feb 2012, 10:37 pm   #169
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Default Re: Bush AC34, no sound.

The resistor you mentioned should measure 470k ohms so it needs to be replaced. From its position it appears to be the V4 control grid resistor (R17 on Trader sheet 1147).

The flash you get on startup with some of the valves is a Mullard/Philips characteristic and does not denote a problem with the valves.

Are the connections to the frame aerial and the tuning capacitor okay?

Gus.
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Old 1st Feb 2012, 10:47 pm   #170
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Default Re: Bush AC34, no sound.

You have problems with the UCH42 again. The reading on pin 3 is way, way too low. It should be about 60 volts.

Check the wave change switch.
Check R6.
Measure the voltage across C14.
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Old 1st Feb 2012, 10:52 pm   #171
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Default Re: Bush AC34, no sound.

Measure the readings on the UCH42 on all three bands.

Cheers,

Steve P.
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Old 2nd Feb 2012, 10:43 am   #172
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Default Re: Bush AC34, no sound.

Quote:
Originally Posted by PJL View Post
The circuit is a bit different from the AC34 and the oscillator anode feed is on a tag strip by the tuning flywheel connected by red wires. It looks like blue grey red? Can you check it's value.
I suggest you follow Steve's advice but can you also measure the voltages either side of this resistor and check the resistor value. Sounds like you may have disturbed some wiring.
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Old 2nd Feb 2012, 9:17 pm   #173
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Default Re: Bush AC34, no sound.

hello lads,
rechecked both UF41 and found my eror on one of the readings,they now read as follows,
1/ pin 1 77.8
pin 8 64.2 difference of 13.6

2/ pin 1 50.6
pin 8 63.7. difference 13.1

re-checked pin 3 UCH42 and again my mistake,reading 99.2 dc on SW and 103.0 on MW
As regards taking readings on all wavebands, I don't have all the knobs for this set so I am not sure which waveband I am on unless I can pick up something. While checking the reading on pin 6 UCH42 I could recieve Radio 5 loud and clear but now its gone again.
I think something is loose somewhere cos sometimes just tapping the tuning knob I can hear stations in the background but as soon as I turn the knob its gone again.
Would the valve seats be faulty? or something else maybe.
Steve/PJL, I will check that tag later
thanks everyone
Bill
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Old 2nd Feb 2012, 10:00 pm   #174
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Default Re: Bush AC34, no sound.

The amended readings for the UF41s show that the heater chain is OK.

The reading on pin 3 of the UCH42 is much better, but I wonder if there is a problem here with the voltage coming and going? Measuring the blue grey red? resistor (6.8K) would be a good idea so that it can be eliminated from out enquiries. Measure the resistance with the set turned off and the voltage on each end with the set turned on.

Don't worry about which waveband the set is set to. Just take readings on the UCH42 in all three?? positions of the wavechange switch.

I wonder whether you have a dodgy wiper on the tuning capacitor. try applying some switch cleaner to the wiper. Also check that there's no axial or radial play in its bearings.
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Old 2nd Feb 2012, 10:38 pm   #175
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Default Re: Bush AC34, no sound.

An improved signal wihen touching the UCH42 grid usually means a problem with the waveband switch or less likely the aerial coils or tuning condensor. I suggest you give the waveband switch another go with Servisol, use an artists brush to get to the back contacts and flick the switch back/forward whilst still damp. Also clean up the valve sockets and pins. 99% of problems are poor contacts.
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Old 6th Feb 2012, 7:32 pm   #176
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Default Re: Bush AC34, no sound.

Hi lads,

Cleaning the waveband switch and valve sockets. Graham,not sure where blue, grey, red resistor is, don't have one of that colour code, also wiper on the tuning cap?
Thanks
Bill
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Old 6th Feb 2012, 8:11 pm   #177
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Default Re: Bush AC34, no sound.

See post #161.

Quote:
Originally Posted by PJL
The circuit is a bit different from the AC34 and the oscillator anode feed is on a tag strip by the tuning flywheel connected by red wires. It looks like blue grey red? Can you check it's value.
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Old 6th Feb 2012, 9:07 pm   #178
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Default Re: Bush AC34, no sound.

Thanks
6.46k ohms
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Old 6th Feb 2012, 9:20 pm   #179
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Default Re: Bush AC34, no sound.

If it's blue, grey, red then it's 6.8K in which case a reading of 6.46K is fine.
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Old 6th Feb 2012, 9:26 pm   #180
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Default Re: Bush AC34, no sound.

I'm not familiar with the construction of the tuning capacitor in this radio. If you look at it you may see some brass colloars on the rotating shaft between the vanes. These will have a groove machined in them and sitting in the groove a springy wiper. Carefully apply Servisol making sure not to get it between the vanes. Then rotate the shaft from stop to stop several times before the cleaner evaporates.
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