BUSH VHF61 no stations

[benjamin77]

Having found myself one in good condition I have recapped it although the main smoothing caps are yet to be done. At the minute I can get no reception and I have tried picking up the local oscillator by using a second set and i cant seem to pick it up.

I have also checked the internal arial connections for breaks and all is ok.

I have thouroughly cleaned the wave change switch as I gather that they can give many problems.

Should I take some valve readings on DC ?

[Steve_P]

Right - no stations and you can't pick up the local oscillator on another station. Does this include VHF? Are the valves lit up?

Switch to P.U. and see if you get anything when you touch the sockets on the back with a wet finger.

And yes please, do take readings on all the valves, DC on the meter, as you have done before.

Cheers,

Steve P.

[benjamin77]

Ok voltages taken on MW with DMM set to DC. I am yet to take readings from valve 1....this in due course.

V2
Pin
1 107v
2 0
3 1.8
4 0
5 0
6 93
7 1.8
8 0
9 1.8

V3
Pin
1 0
2 0
3 1
4 0
5 0
6 0
7 180
8 102
9 0

V4
Pin
1 0
2 0
3 1.7
4 0
5 0
6 0
7 175
8 151
9 0

V5 pin1-8 0v pin9 70v

V6
Pin
1 1.8v
2 1.8
3 7
4 0
5 0
6 7.5
7 241
8 0
9 217

V7
Pin
1 4.8
2 0
3 254
4 0
5 0
6 0
7 5
8 0
9 0

nothing on FM or when the P/U connections are touched with a wet finger....

[benjamin77]

Ok now switched to FM and checked pins for voltages. Although the valve is glowing the readings are very low
Pins 1 and 6 0.75v
all others 0v

Surely this cant be right....maybe its me ?

[Steve_P]

Measure V7 again on VHF and MW. There should be volts on 2 pins. As there is nothing on one of the pins and HT to the rest of the set, I'm a bit worried by that.

Cheers,

Steve P.

[Steve_P]

Hang on - which sheet are you using?

Cheers,

Steve P.

[benjamin77]

Steve I am using the Manufacturers service sheet, just checked again for HT on another pin at V7. Looking at the wiring I think it should Pin1 as this is fed direct from the mains trannie.

DMM set to DC i can't get a reading but set to AC its comes out as 238v.

[PJL]

I assume the readings were taken in VHF as the oscillator anode V3 pin 8 is 0V. I suggest we try to get it workin gon AM first.

I have the manufacturers sheet here and I think there is a bit of confustion over numbers. V6 above looks like the output and V7 the indicator. If this is true and you have replaced C56 then the EL84 has some grid leak as it is showing 1.8V but probably not enough to matter.

Otherwsie all looks good and HT is correct...

[Steve_P]

Have you checked the speaker connections etc?
Do you get any noise in the speaker when you operate the wavechange buttons?
Does it make any noise or is it completely silent?

Cheers,

Steve P.

[benjamin77]

There is some output at the speaker I.e cackle when the volume pot is turned and when the wave change switches are changed. With regards to what PJL says about the manufacturers sheet it is confusing as it shows 8 valves in the valve line up but they have missed out valve 7 in the chassis photo's.. Hmm....

I am thinking that maybe the volume pot and wave change switches are the problem ?

[Steve_P]

I'm going to take a leap now - replace the VHF valve first - ECC85.

Cheers,

Steve P.

[TimS]

The 'eighth' valve is probably the magic eye on the speaker board (EM81).

Are you getting MW/LW reception? If not, then its unlikely to be the ECC85 causing problems as this valve is used for VHF only, although you will find its heaters are kept on all the time. Just to make absolutely sure you could remove the ECC85 - the set will work fine without it on MW/LW.

I'd only suspect the vol pot if you get alot of crackling - its quite normal to have noisy contacts due to dirt accumulated over the years. I use Electrolube contact cleaner on those and wavechange switches.

-- Tim.

[Steve_P]

Mine was like this - 2 faults on it. The ECC85 and a cap on the AM oscillator.

The ECC85 isn't the most reliable valve on earth by any means, and always worth swapping over as a check for VHF.

Cheers,

Steve P.

[TimS]

I have recapped it although the main smoothing caps are yet to be done

Forgot to mention - I have 5 post-war Bush sets - all still have their original smoothing caps. If they haven't gone bang yet they are probably OK!

[benjamin77]

Cheers guys for all your help. I am now routing through 3 large boxes of pulled valves for a replacement.

There must be one in there somewhere......

P.s thought I found one but its a UCC85....... Ho hum

[PJL]

Benjamin, hold on for a bit on the replacement valve and concentrate on AM. The ECC85 is only used by VHF. As all the other voltages look correct, the valves all seem to be working OK.

Switch to AM and check V3 pin 8. If it is still zero clean the switch.

My VHF61 had a faulty IFT (capacitor failure). Do you have a signal generator?

[benjamin77]

I dont have a signal generator , what if I connected up another radio from its second speaker socket to gram input of the Bush. If the sound gets out at least I can rove that the output stages are ok ?

[PJL]

Measure V3 pin 8 when switched to AM first...you may not need it.

[benjamin77]

Right back on this job again> I have just connected up another set from its Ext speaker socket to the Gram input of the Bush and the sound comes out of the speaker.

Therefore am i correct in saying that its probably the wavechange switch casuing the probelm ? There is also a lot of crackleing and popping when I use the wave change switches. Although I have cleaned them previously....

[Steve_P]

Well I still think it's worth trying another ECC85 if you've got one to hand.

Get another radio, a tranny would be best, and see if you pick up the oscillator of the VHF61 on it. Tune the test radio between Virgin and Talk Sport. (Better than being on Talk Sport.)

The IF on this set is 470 kHz, so tune about round where 5 Live should be (433 Metres, 696 KHz) and see if you can pick up the oscillator on the test set.

The test set will need to be very close to the set, but it will tell you if the Oscillator is working.

Cheers,

Steve P.