KB QV40 Fringe Version - Request for advice. - UK Vintage Radio Repair and Restoration Discussion Forum

DoctorWho · 30th Apr 2007, 11:19 am

I'm working on a set with our friend Tim who is currently staying with us, he's bought a KB QV40 Fringe Version TV set, looking at the date on the condensers it seems to be circa 1959.

The nearest service data we can find for this set is Trader Sheet 1457, this is not the same set, but it is similar.

We changed all of the old wax condensers and most of the electrolyitcs, the set now powers up with a good raster, good brightness etc.

The only problem we have is that we have no signal being received. When the tuner is turned through the 13 channels there is absolutely nothing happening on the screen, nothing to show that the tuner is being turned. The 2 valves in the tuner are glowing and so is the 9D7 (all of the valves are glowing for that matter). There are 2 valves in the tuner, which is a very small and compact tuner, possibly a high gain tuner, as this is a fringe version of the set.

Can anyone suggest what the problem is likely to be here please? Is the 9D7 likely to be the cause? If so, is there any equivalent to the 9D7?

Thanks in advance for any help or advice.

Peter.

Steve_P · 30th Apr 2007, 11:43 am

First thing - Check what you've already done. It's easy to make a mistake!

Check the coils in the tuner are present and right. Does the set make any sounds (clicks, etc) when the tuner is turned. Is the knob making contact!

Check voltages round the valves - are they there. Just because a valve is Lit Up doesn't mean it's working!

If you can't find the problem from that, come back with more info.

Cheers,

Steve P

FERNSEH · 30th Apr 2007, 11:47 am

Hi Peter,
The Brimar 9D7 is the vari-mu version of the 6BW7 RF pentode. I think that it is a difficult valve to find these days. The EF85 or 6F26 will serve as a suitable replacement.

DFWB.

DoctorWho · 30th Apr 2007, 12:24 pm

Steve - Thanks for your reply. The set doesn't make any sounds at all when the tuner is turned, and there's nothing going on visually either. We'll certainly double check the work which has been done again. If we can't find anything we'll take some voltage readings as you suggest.

David - Thanks for your help. It's very useful to know that we can use an EF85 etc instead, thank you. Is the 9D7 a valve likely to be low?

I'll report back later on when we've had another look at the set this evening.

Thanks again,

Peter.

FERNSEH · 30th Apr 2007, 3:23 pm

Hello Peter, The voltages at the base of the 9D7 should be under no signal conditions.
Anode pin 7 210 volts, screen grid pin 8 120 volts and the cathode pin 3 should be about 1 volts.
The anode voltage for the V3 (9D7) is supplied though R37 (3.3Kohms 1W) and the screen grid is supplied though R33 which is a 27Kohm 1 watt resistor, this could have gone high resistance or OC.
Also, check the HT supply to the tuner, this is supplied though R32 which is a 1.2Kohms 3 watt resistor.

For a quick test an EF80 can be tried to determine if the 9D7 has gone faulty.

DoctorWho · 30th Apr 2007, 3:31 pm

Thanks David, that's extremely useful, we'll do some investigating this evening and I'll let you know what we discover.

Peter.

Ed_Dinning · 30th Apr 2007, 8:13 pm

Hi Peter, if you have access to a signal generator you could try tuning through the IF frequency and see if there is any response from sound or vision.

Ed

DoctorWho · 30th Apr 2007, 8:36 pm

I have one for radio use Ed, but not for TV. I'll see if we can do anything along the lines you suggest.

Thanks for the help.

Peter.

Heatercathodeshort · 30th Apr 2007, 8:59 pm

Hello Peter,
I am having to write this in almost complete darkness. I accidentally posted my application to the Victorian Home for Faded Television Engineers with the gas bill. I have been scared to go out in case I am whisked off the street by some sinister guys with white coats........
Now your KB OV40. I think the tuner used in this series was the 'Fireball'. If it is cylinder shaped, it certainly is. A common fault with these was failure of the co-ax i.f output lead and another horror to find was a disintegrated lead out wire to the anode of the tuner mixer valve [PCF80?] from the I.F. output transformer. This is a very small coil assembly and will have to be examined with great care. The wire is very thin. I have a tuner somewhere to hand and can take a picture of the offending coil if this will help. Another version of the set used a very small unit but these were rare. You say you have a radio signal generator? As Ed suggests you can connect its output via a small capacitor to the control grid of the 9D7. Turn the generators output on full and make sure the modulation is on [Tone]. Swing the output frequency slowly from the lowest to highest and if the common I.F. stage is working you should get some hum bars on the screen and some tone from the speaker even if the signals injected are well off the 38mc/s required.
Fernseh has described the next move if the signals are absent. If present you will have to check the tuner voltages as suggested. If the tuner valves have been accidentally interchanged a resistor will be cooked in the tuner. Its worth checking this. Its unusual to get absolutely no response from a tuner when changing channels. Dare I suggest a component on the wrong tag.....Oh stop it John.. Regards John.

DoctorWho · 1st May 2007, 9:15 am

Oh dear John, now that's not good, you'd better plead ignorance when they arrive to take you away......

Thanks for your help with this. One big problem is that the set my friend has, the QV40, is not covered in any of the service data, there's the QV30 but none of the sets on any of the Trader sheets is exactly the same as the QV40. As I mentioned above we're using Trader Sheet 1457, but beneath the chassis the circuit is very different.

Does anyone have the correct data for the QV40 please?

The set does indeed have a Fireball tuner. Thanks for pointing out the weak points in this tuner and it's leads, we'll check those out next. If a picture of the coil is possible it would be appreciated. The HT is present at the tuner.

We spent a while going through the set last night, we found a number of hisg resistors, and these were replaced.

We do have one problem, and that is a loose wire, which looks to have been hanging loose for years, as the end had gone very dark. It comes from the PCB, Pin 6 of the PCL85 and is a brown coloured wire, it heads vaguely in the direction of the ECC82. Any ideas where this should be connected?

The PCB on this set is quite different to the PCB on the QV30, so there are a lot of things we can't locate accurately due to the service data being incorrect.

Any further thoughts appreciated.

Peter.

FERNSEH · 1st May 2007, 11:01 am

Hello Peter,
For all intents and purposes the IF amplifier stages of the QV40 are similar to those in the QV30. The QV40 employes a CG12 crystal diode as the video detector and in the QV30 it is one half of a 6AL5/EB91.

The QV30 employs a miniature turret tuner.

DFWB.

DoctorWho · 1st May 2007, 11:43 am

Thanks David, I think we were a bit puzzled when we started work on the underside of the chassis and found out that the layout and valve positions are quite different from the QV30 Trader Sheet. Do you happen to know if any QV40 service data was actually issued?

Steve_P · 1st May 2007, 1:17 pm

Yes, it was issued. It's in Newness 1960/61 book. Circuit on page 460. I'll have to ask before I post it, as I got in a bit of trouble last time!

By the way, check R31. 1.2K. Feeds current to the tuner!! Should be 162 Volts if there is no signal, 170 Volts if there is.

Cheers,

Steve P.

DoctorWho · 1st May 2007, 1:42 pm

Thanks Steve, I would really appreciate that if it's possible.

Thanks for the advice re R31, we'll check that.

All the best,

Peter.

DoctorWho · 1st May 2007, 7:10 pm

It may have got missed above, but any ideas where the brown lead, hanging lose from pin 6 of the PCL85 should go please?

Peter.

FERNSEH · 1st May 2007, 9:21 pm

Hello Peter,
You mention that your set has a PCL85 valve. According to the information in the 1960-61 Newnes R & T servicing book the frame output valve V6 is a PCL82, so is the sound output valve V8.
The video output valve V5 is a PCL84. In both valves pin 6 is the pentode section anode.
I don't think the PCL85 was ever used in this set, or was there a modified receiver, QV40/1?

DFWB

DoctorWho · 1st May 2007, 10:05 pm

Hello David,

Thanks for your reply. Well this set certainly has a PCL85 in it, and, as far as I can see it is not a modified set.

We are really quite stuck as we do not have the corrrct service data for this set, if anyone at all can E-mail me a scan of the data from the Newnes manual I would be extremely grateful.

I am wondering if the PCL82 was mistakenly replaced by a PCL85? What would this cause?

We have now got sound, but with interference, and vision, but with multiple imaging and inability to lock line or frame - see attached picture. You can just about see parts of Testcard C in multiple going from side to side, but you can't make it out clearly or stabilise it.

Any further advice greatly appreciated, and any help with the correct service data appreciated.

Thanks again,

Peter.

DoctorWho · 1st May 2007, 10:10 pm

My mistake, the valve is a PCF80 on the PCB which has the brown wire on Pin 6 which does not go anywhere.

Any advice on the correct position of the other end of this wire would be appreciated. We think the problem may be related to fold over?

This picture shows what happens if you turn the line hold control further. Does this suggest anything else?

Thanks again,

Peter.

Dave Moll · 1st May 2007, 10:54 pm

According to my book, pin 6 (pentode anode) of V10 (PCF80 - synch sep & afc) connects to R130 (82K) and C57 (0.1uF - in video amp/vert synch amp). I hope that helps.

FERNSEH · 2nd May 2007, 1:03 am

Hello Peter,
The triode section of the PCF80 is described as "AFC" in the KB circuit diagram. Actually it is a coincidence detector. The anode is supplied with a pulse from the line output transformer and the line sync pulses are supplied to the triode grid. A control voltage from the AFC valve is fed to the grid (pin2) of one of the sections of the double triode line oscillator valve (12AU7/ECC82).

The original KB circuit diagram of the line AFC is drawn in a confusung manner.
It might be better to redraw it to clarify how the circuit works.

DFWB.

30th Apr 2007, 11:19 am	#1
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	KB QV40 Fringe Version - Request for advice. I'm working on a set with our friend Tim who is currently staying with us, he's bought a KB QV40 Fringe Version TV set, looking at the date on the condensers it seems to be circa 1959. The nearest service data we can find for this set is Trader Sheet 1457, this is not the same set, but it is similar. We changed all of the old wax condensers and most of the electrolyitcs, the set now powers up with a good raster, good brightness etc. The only problem we have is that we have no signal being received. When the tuner is turned through the 13 channels there is absolutely nothing happening on the screen, nothing to show that the tuner is being turned. The 2 valves in the tuner are glowing and so is the 9D7 (all of the valves are glowing for that matter). There are 2 valves in the tuner, which is a very small and compact tuner, possibly a high gain tuner, as this is a fringe version of the set. Can anyone suggest what the problem is likely to be here please? Is the 9D7 likely to be the cause? If so, is there any equivalent to the 9D7? Thanks in advance for any help or advice. Peter.

30th Apr 2007, 11:43 am	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: KB QV40 Fringe Version - Request for advice. First thing - Check what you've already done. It's easy to make a mistake! Check the coils in the tuner are present and right. Does the set make any sounds (clicks, etc) when the tuner is turned. Is the knob making contact! Check voltages round the valves - are they there. Just because a valve is Lit Up doesn't mean it's working! If you can't find the problem from that, come back with more info. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

30th Apr 2007, 11:47 am	#3
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: KB QV40 Fringe Version - Request for advice. Hi Peter, The Brimar 9D7 is the vari-mu version of the 6BW7 RF pentode. I think that it is a difficult valve to find these days. The EF85 or 6F26 will serve as a suitable replacement. DFWB.

30th Apr 2007, 12:24 pm	#4
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Steve - Thanks for your reply. The set doesn't make any sounds at all when the tuner is turned, and there's nothing going on visually either. We'll certainly double check the work which has been done again. If we can't find anything we'll take some voltage readings as you suggest. David - Thanks for your help. It's very useful to know that we can use an EF85 etc instead, thank you. Is the 9D7 a valve likely to be low? I'll report back later on when we've had another look at the set this evening. Thanks again, Peter.

30th Apr 2007, 3:23 pm	#5
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: KB QV40 Fringe Version - Request for advice. Hello Peter, The voltages at the base of the 9D7 should be under no signal conditions. Anode pin 7 210 volts, screen grid pin 8 120 volts and the cathode pin 3 should be about 1 volts. The anode voltage for the V3 (9D7) is supplied though R37 (3.3Kohms 1W) and the screen grid is supplied though R33 which is a 27Kohm 1 watt resistor, this could have gone high resistance or OC. Also, check the HT supply to the tuner, this is supplied though R32 which is a 1.2Kohms 3 watt resistor. For a quick test an EF80 can be tried to determine if the 9D7 has gone faulty.

30th Apr 2007, 3:31 pm	#6
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Thanks David, that's extremely useful, we'll do some investigating this evening and I'll let you know what we discover. Peter.

30th Apr 2007, 8:13 pm	#7
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,196	Re: KB QV40 Fringe Version - Request for advice. Hi Peter, if you have access to a signal generator you could try tuning through the IF frequency and see if there is any response from sound or vision. Ed

30th Apr 2007, 8:36 pm	#8
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. I have one for radio use Ed, but not for TV. I'll see if we can do anything along the lines you suggest. Thanks for the help. Peter.

30th Apr 2007, 8:59 pm	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: KB QV40 Fringe Version - Request for advice. Hello Peter, I am having to write this in almost complete darkness. I accidentally posted my application to the Victorian Home for Faded Television Engineers with the gas bill. I have been scared to go out in case I am whisked off the street by some sinister guys with white coats........ Now your KB OV40. I think the tuner used in this series was the 'Fireball'. If it is cylinder shaped, it certainly is. A common fault with these was failure of the co-ax i.f output lead and another horror to find was a disintegrated lead out wire to the anode of the tuner mixer valve [PCF80?] from the I.F. output transformer. This is a very small coil assembly and will have to be examined with great care. The wire is very thin. I have a tuner somewhere to hand and can take a picture of the offending coil if this will help. Another version of the set used a very small unit but these were rare. You say you have a radio signal generator? As Ed suggests you can connect its output via a small capacitor to the control grid of the 9D7. Turn the generators output on full and make sure the modulation is on [Tone]. Swing the output frequency slowly from the lowest to highest and if the common I.F. stage is working you should get some hum bars on the screen and some tone from the speaker even if the signals injected are well off the 38mc/s required. Fernseh has described the next move if the signals are absent. If present you will have to check the tuner voltages as suggested. If the tuner valves have been accidentally interchanged a resistor will be cooked in the tuner. Its worth checking this. Its unusual to get absolutely no response from a tuner when changing channels. Dare I suggest a component on the wrong tag.....Oh stop it John.. Regards John.

1st May 2007, 9:15 am	#10
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Oh dear John, now that's not good, you'd better plead ignorance when they arrive to take you away...... Thanks for your help with this. One big problem is that the set my friend has, the QV40, is not covered in any of the service data, there's the QV30 but none of the sets on any of the Trader sheets is exactly the same as the QV40. As I mentioned above we're using Trader Sheet 1457, but beneath the chassis the circuit is very different. Does anyone have the correct data for the QV40 please? The set does indeed have a Fireball tuner. Thanks for pointing out the weak points in this tuner and it's leads, we'll check those out next. If a picture of the coil is possible it would be appreciated. The HT is present at the tuner. We spent a while going through the set last night, we found a number of hisg resistors, and these were replaced. We do have one problem, and that is a loose wire, which looks to have been hanging loose for years, as the end had gone very dark. It comes from the PCB, Pin 6 of the PCL85 and is a brown coloured wire, it heads vaguely in the direction of the ECC82. Any ideas where this should be connected? The PCB on this set is quite different to the PCB on the QV30, so there are a lot of things we can't locate accurately due to the service data being incorrect. Any further thoughts appreciated. Peter.

1st May 2007, 11:01 am	#11
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: KB QV40 Fringe Version - Request for advice. Hello Peter, For all intents and purposes the IF amplifier stages of the QV40 are similar to those in the QV30. The QV40 employes a CG12 crystal diode as the video detector and in the QV30 it is one half of a 6AL5/EB91. The QV30 employs a miniature turret tuner. DFWB.

1st May 2007, 11:43 am	#12
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Thanks David, I think we were a bit puzzled when we started work on the underside of the chassis and found out that the layout and valve positions are quite different from the QV30 Trader Sheet. Do you happen to know if any QV40 service data was actually issued?

1st May 2007, 1:17 pm	#13
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: KB QV40 Fringe Version - Request for advice. Yes, it was issued. It's in Newness 1960/61 book. Circuit on page 460. I'll have to ask before I post it, as I got in a bit of trouble last time! By the way, check R31. 1.2K. Feeds current to the tuner!! Should be 162 Volts if there is no signal, 170 Volts if there is. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

1st May 2007, 1:42 pm	#14
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Thanks Steve, I would really appreciate that if it's possible. Thanks for the advice re R31, we'll check that. All the best, Peter.

1st May 2007, 7:10 pm	#15
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. It may have got missed above, but any ideas where the brown lead, hanging lose from pin 6 of the PCL85 should go please? Peter.

1st May 2007, 9:21 pm	#16
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: KB QV40 Fringe Version - Request for advice. Hello Peter, You mention that your set has a PCL85 valve. According to the information in the 1960-61 Newnes R & T servicing book the frame output valve V6 is a PCL82, so is the sound output valve V8. The video output valve V5 is a PCL84. In both valves pin 6 is the pentode section anode. I don't think the PCL85 was ever used in this set, or was there a modified receiver, QV40/1? DFWB

1st May 2007, 10:05 pm	#17
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. Hello David, Thanks for your reply. Well this set certainly has a PCL85 in it, and, as far as I can see it is not a modified set. We are really quite stuck as we do not have the corrrct service data for this set, if anyone at all can E-mail me a scan of the data from the Newnes manual I would be extremely grateful. I am wondering if the PCL82 was mistakenly replaced by a PCL85? What would this cause? We have now got sound, but with interference, and vision, but with multiple imaging and inability to lock line or frame - see attached picture. You can just about see parts of Testcard C in multiple going from side to side, but you can't make it out clearly or stabilise it. Any further advice greatly appreciated, and any help with the correct service data appreciated. Thanks again, Peter. Attached Thumbnails

1st May 2007, 10:10 pm	#18
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: KB QV40 Fringe Version - Request for advice. My mistake, the valve is a PCF80 on the PCB which has the brown wire on Pin 6 which does not go anywhere. Any advice on the correct position of the other end of this wire would be appreciated. We think the problem may be related to fold over? This picture shows what happens if you turn the line hold control further. Does this suggest anything else? Thanks again, Peter. Attached Thumbnails Last edited by DoctorWho; 1st May 2007 at 10:33 pm.

1st May 2007, 10:54 pm	#19
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,131	Re: KB QV40 Fringe Version - Request for advice. According to my book, pin 6 (pentode anode) of V10 (PCF80 - synch sep & afc) connects to R130 (82K) and C57 (0.1uF - in video amp/vert synch amp). I hope that helps. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

2nd May 2007, 1:03 am	#20
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: KB QV40 Fringe Version - Request for advice. Hello Peter, The triode section of the PCF80 is described as "AFC" in the KB circuit diagram. Actually it is a coincidence detector. The anode is supplied with a pulse from the line output transformer and the line sync pulses are supplied to the triode grid. A control voltage from the AFC valve is fed to the grid (pin2) of one of the sections of the double triode line oscillator valve (12AU7/ECC82). The original KB circuit diagram of the line AFC is drawn in a confusung manner. It might be better to redraw it to clarify how the circuit works. DFWB.