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Old 18th Jan 2012, 10:36 pm   #121
Steve_P
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Default Re: Bush AC34, no sound.

Well the volts on Pin 2 are back. And pin 5, although they are maybe a touch low!

There should not be anything on Pin 4 surely, as there is no connection. There also should be 8 volts on the Cathode, which we don't see. (Pins 3 and 7).

With the set off, there should be 220 Ohms (may be a bit higher) between Chassis and Pin 3/7.

The UL41 is probably knackered now, so lets get the rest right and then you can get a UL41 (Graham!)

Cheers,

Steve P.
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Old 18th Jan 2012, 10:47 pm   #122
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Default Re: Bush AC34, no sound.

OK.

We now have HT on the UL41 anode which is good.

There are three problems though.

Voltage on the UY41 Heater is 158.6-116.1=42.5V it should be 31V.
Voltage on the UL41 Heater is 116.2. 98.4=17.8V it should be 45V
Voltage on UL41 cathode is low. It should be about 8V.

Low voltage on UL41 cathode indicates no anode or screen current. This may be down to the low heater voltage reducing the valve's emission.

Try this. Switch off. Pull out all the valves. Measure the resistance to chassis of each heater pin. (The brown wires). All bar two pins should read infinite resistance or open circuit.
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Old 18th Jan 2012, 10:52 pm   #123
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Default Re: Bush AC34, no sound.

Bill.

PM me your address and I'll post a UL41 to you FOC.
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Old 19th Jan 2012, 12:32 am   #124
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Default Re: Bush AC34, no sound.

Best to leave powered off till the new UL41 arrives as the HT is high and the other valves are under stress but it looks promising and hopefully we should have some sound.

Next problem is the oscillator which isn't according to the voltage readings. Have you cleaned the wavechange switch? If not this is a job that can be done in the meantime. Servisol is the best stuff.
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Old 19th Jan 2012, 6:31 pm   #125
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Default Re: Bush AC34, no sound.

A used tested UL41 is on its way to Bill.
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Old 19th Jan 2012, 8:39 pm   #126
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Default Re: Bush AC34, no sound.

Hi lads,
Readings from heater pins with all valves removed
UY41
Pin 1 40.3 ohms
UBC41
pin 1 1.6 ohms
No reading on any other pin

Bill
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Old 19th Jan 2012, 9:32 pm   #127
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Default Re: Bush AC34, no sound.

That sounds about right.
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Old 23rd Jan 2012, 2:21 pm   #128
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Default Re: Bush AC34, no sound.

Hi lads,
A very big thanks to Graham
Valve arrived in post this morning....I will fit it tonight and post

Bill
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Old 23rd Jan 2012, 8:00 pm   #129
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Default Re: Bush AC34, no sound.

Hi lads,
Good news and bad news. Fitted valve OK all lighting, now getting sound from speaker but it's only a low hum. I tried running through the tuning bands to see if I could pick up anything but nothing only the hum.
Bill
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Old 23rd Jan 2012, 8:04 pm   #130
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Default Re: Bush AC34, no sound.

Lets have a set of voltage readings again with the waveband switch in the MW position.

That was expected as the local oscillator was not working before. Did you clean the waveband switch? If not, do it before taking the voltage readings.
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Old 23rd Jan 2012, 8:30 pm   #131
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Default Re: Bush AC34, no sound.

Hi PJL ,
I blew out any dust and debris ,used some switchclean. I didn't take the wave band switch apart, do I need to do this?
Bill
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Old 23rd Jan 2012, 9:53 pm   #132
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Default Re: Bush AC34, no sound.

Nope, switch cleaner should do the job. Select MW and take the readings and let's see what we have.
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Old 23rd Jan 2012, 11:51 pm   #133
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Default Re: Bush AC34, no sound.

Looking at your previous voltages I think we have some other significant circuit differences around the oscillator. The AC34 took the oscillator HT feed from the pentode screen grid but your measurements show:
pentode screen = 133V
triode anode = 59.7V
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Old 24th Jan 2012, 12:03 am   #134
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Default Re: Bush AC34, no sound.

Ok I will get the readings and post

Bill
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Old 24th Jan 2012, 11:43 am   #135
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Default Re: Bush AC34, no sound.

Hi lads,
Voltage readings

UY41
Pin 1 brown 160.5 ac (Heater)
Pin 2 red 259.0 ac (Anode)
Pin 3,4,5,6 blank
Pin 7 red 285.6 dc (Cathode)
Pin 8 brown 126.9 ac (Heater)

UL41
Pin 1 brown 126.6 ac (Heater)
Pin 2 blue 270.4 dc (Anode)
Pin 3 blank
Pin 4 green 1.09 dc (Termination point)
Pin 5 red 133.2 dc (Screen Grid)
Pin 6 blank (Control Grid)
Pin 7 yellow 9.85 dc (Cathode)
Pin 8 brown 79.2 ac (Heater)

UBC 41
Pin 1 brown 9.41 ac (Heater)
Pin 2 blue 88.9 dc (Anode)
Pin 3 to volume control, loud noise from speaker when checking this pin (Control Grid)
Pin 4 0.0 (Shield)
Pin 5 0.0 (Anode D2)
Pin 6 green 0.11 ac (Anode D1)
Pin 7 yellow 1.4 dc (Cathode)
Pin 8 brown 23.52 ac (Heater)

UF41
Pin 1 brown 79.2 ac (Heater)
Pin 2 orange 248.0 dc (Anode)
Pin 3,4 blank I/Cs
Pin 5 purple 46.4 dc (Screen Grid)
Pin 6 resistor 0.01 A (Control Grid)
Pin 7 yellow 1.05 dc (Cathode)
Pin 8 brown 65.4 ac (Heater)

UF41
Pin 1 brown 52.0 ac (Heater)
Pin 2 blue 98.0 dc (Anode)
Pin 3,4 blank I/Cs
Pin 5 purple 84.7 (Screen Grid)
Pin 6 green 0.1 ac (Control Grid)
Pin 7 yellow 0.86 dc (Cathode)
Pin 8 brown 65.0 ac (Heater)

UCH42
Pin 1 brown 23.5 ac (Heater)
Pin 2 blue 131.6 dc (Anode of hexode section)
Pin 3 green 104.4 dc (Anode of triode secton)
Pin 4 resistor 0.0 (Control Grid of triode section))
Pin 5 purple 46.6 dc (G2 & G4, screen grids of hexode section)
Pin 6 green 0.01 ac (Control Grid of hexode section)
Pin 7 yellow 1.28 dc (Common Cathode)
Pin 8 brown 38.2 ac (Heater)

Magic eye
Pin 1 Brown 51.3 ac (Heater)
Pin 2 blank
Pin 3 red 233.0 dc
Pin 4 green 3.01 ac
Pin 5 brown 37.9 ac (Heater)

Hope these are some help
Thanks
Bill
Pin 2
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Old 24th Jan 2012, 11:50 am   #136
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Default Re: Bush AC34, no sound.

That's looking better! Bin the old UL41. I'm analysing the readings.
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Old 24th Jan 2012, 12:27 pm   #137
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Default Re: Bush AC34, no sound.

The voltage on pin 3 (anode of triode section) of the UCH42 is high indicating that it isn't oscillating. It should read about 60 VDC, but you show 104.4 VDC. Measure the value of R6 which should be 15K. (Brown, Green, Yellow).
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Old 24th Jan 2012, 12:38 pm   #138
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Default Re: Bush AC34, no sound.

As PJL indicated in post #133 your UCH42 doesn't seem to be wired in the same manner as the Bush AC34. This could be a design difference, or another "missing link". We'd better have some pictures showing the wiring of the UCH42 and its conections to the tag strip.
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Old 24th Jan 2012, 4:03 pm   #139
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Default Re: Bush AC34, no sound.

Hi lads,
I have taken some pics....the area is a bit cluttered and difficult to photo,so I have taken a few and a sketch as best as I can see

Bill
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Old 24th Jan 2012, 4:11 pm   #140
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Default Re: Bush AC34, no sound.

Could you clarify where pin 2 (Blue wire) goes to. Your sketch says "BASE OF" I think.
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