Old VHS Camcorder

[loopyloo]

Does anyone know the whereabouts of a service manual for a Philips VKR6855 ?

It seems to have 2 problems :
1/ The cassette section sometimes hums for a bit then the unit shuts off. I'm guessing it needs a belt or tyre somewhere.
2/ The viewfinder display doesn't work. Reason unknown but I can't figure out how to get the thing off the camera to pull it apart.

[loopyloo]

I found a plastic latch almost hidden and was able to dismantle the viewfinder. Nothing visibly bad in there.
Is there a common fault that these tiny crt's inherit ?

[TVguy]

If this is a full size VHS camcorder, then it is most likely a Panasonic NV-M7 OEM variant.
Philips never released any of their own designs in Australia AFAIK. Even their VHS recorders were all OEM, Sharp originally, then in later years JVC.

[loopyloo]

If this is a full size VHS camcorder, then it is most likely a Panasonic NV-M7 OEM variant.
Philips never released any of their own designs in Australia AFAIK. Even their VHS recorders were all OEM, Sharp originally, then in later years JVC.

Thanks for that. You were spot-on as usual.
I found a Pana manual and it does look the same.
Now to go fault searching.

By the way, do you recognise this plug ?
It measures 10mm in the long direction and has 3 flat pins.



The camcorder came with everything except the power cable that goes from the charger directly to the camcorder, it also included 2 buggered lead acid batteries.
I figure I might crack one of them open and fill it with NIMH's, but in the mean time, if I make a power cable it would be useful.

[TVguy]

From memory, the Pana units never came with anything other than the charger and two batteries. The multi-pin "ADAPTOR" connector carried AV and power.
Customers would constantly break the pins; it was a good money earner replacing the cable (although a prick of a job)!
Fairly sure that I threw out one of these units in a recent purge of my clutter; need to check as I may have had second thoughts about discarding the camcorder. It was complete in the hard case with every accessory.
This was Panasonic's second model using a CCD image sensor (after the NV-M5). I spent two weeks training at Panasonic learning about Bayer filters, Bimorph Piezo strip actuators and was introduced to the Femtofarad.
All that effort, now just a distant memory of a time when great change was happening in the world of electronics.
Thankfully the grass roots learning has enabled me to continue to ply my trade. Refrigeration, comfort air, appliances and AV products are all part of my work portfolio now, but without doubt, electronics is the bedrock.
I'll try to scour the mayhem that is my workshop for the M7; maybe I did keep it? Unfortunately SWMBO tends to decree that which is destined for the scrap heap!

[loopyloo]

I cracked open the viewfinder and connected gnd and 5v to it.
Appears dead. Shouldn't I be able to see the heater glowing ?

[lsemmens]

I hope you're only trying to resurrect this just for fun............

[tristen]

I hope you're only trying to resurrect this just for fun............

Why??

I continue repair old equipment for people for a variety of reasons.

It might have sentimental value or similar.

You might take it on as a challenge or for other personal reasons.

Yes, the risk of future breakdown due to other component failure can be a deterrent to repairing old equipment, but one has to use discretion in such matters. In particular, inform the customer/acquaintance/friend that a guarantee cannot be given due to the equipment's age.

If a paying customer, economics also comes into the equation, but again, warn them.

There are more things to consider than economics. It could be argued that I am not worth repairing due to age, but I have a vested interest therefore strongly contest that attitude/policy

[loopyloo]

I hope you're only trying to resurrect this just for fun............

Well of course.
Why else would I get involved with such a lame brained project ? ... Lol

[loopyloo]

Things I've found out so far :

1/ The viewfinder doesn't work.

With the cam connected to my TV via A/V connectors :
2/ The CCD shows on the TV with a reasonable picture and in colour.
3/ Playback of a video shot with the cam is in black & white.
4/ Playback of a movie on tape "Red Dragon" was in black & white but "Babe" was black & white with faint coloured bars over the top of it (like the picture I drew below).
5/ Playback sound is very low.

[lsemmens]

Why??

I continue repair old equipment for people for a variety of reasons.

It might have sentimental value or similar.

You might take it on as a challenge or for other personal reasons.

Yes, the risk of future breakdown due to other component failure can be a deterrent to repairing old equipment, but one has to use discretion in such matters. In particular, inform the customer/acquaintance/friend that a guarantee cannot be given due to the equipment's age.

If a paying customer, economics also comes into the equation, but again, warn them.

There are more things to consider than economics. It could be argued that I am not worth repairing due to age, but I have a vested interest therefore strongly contest that attitude/policy

I have no problem with any of your reasoning. I just find it "strange" (couldn't think of a better word) that a person would want to resurrect an outdated technology for any other reason than their enjoyment. Unless, of course, it is part of a "museum" display.

[loopyloo]

I have no problem with any of your reasoning. I just find it "strange" (couldn't think of a better word) that a person would want to resurrect an outdated technology for any other reason than their enjoyment. Unless, of course, it is part of a "museum" display.

There are 2 reasons for fixing this, the first is the appetite I have for learning something. The second is, I'm an always broke pensioner and if I can fix it I will sell it to fund my other projects that keep my mind busy.

[loopyloo]

This is the viewfinder CRT circuit.
With 5volts connected at P701 :
150mV at the heater pins 2 and 3 (H&HK)

With no power :
The heater reads around 2 ohms
Transistors test ok
D702 reads (tested in circuit) much the same both directions. It's a low loss super high speed rectifier. What is the purpose of this diode in this circuit ? Can I remove it then power up to see if it was pulling the circuit down ?

[TVguy]

[QUOTE=loopyloo;722064]This is the viewfinder CRT circuit.
With 5volts connected at P701 :
150mV at the heater pins 2 and 3 (H&HK)

...What is the purpose of this diode in this circuit ? Can I remove it then power up to see if it was pulling the circuit down ?

Clearly the horizontal scanning circuit is not functional. D702 cannot be removed with the circuit energised.
It is the efficiency diode responsible for the first half of horizontal scanning. In conjunction with flyback tuning capacitor C714, it clamps the negative excursion of the resonant circuit and gradually discharges the energy stored in the bulk inductance of the scan coils and FBT to allow the magnetic field to decay at a predetermined rate; thus completing phase four of four sequence scanning. Removing it will certainly be destructive as the resonant oscillations will not be damped.
Sadly, in true Pana style the circuit has been drawn incorrectly (note that it shows the vertical oscillator driving the horizontal output on pin 22???).
Look at the scan coupling capacitor C712 and horizontal drive dump capacitor C711. The horizontal output transistor Q702 needs a decent base current to get it inspired to amplify. If the electrolytic capacitors are small can aluminium types, they will have gone to God.
Forget active testing and check all electros with an ESR meter. This is a labour of love and you need to make haste slowly.

The small video drum on these units used four video heads to achieve a full frame scan. The image you have presented would indicate either complete head wear failure, or more likely LV power supply issues. Those horrid can electros had a tendency to fail in an unenergised state. Recapping these is not for the faint-hearted, as the electrolyte can leak and damage PCB traces and vias.

BTW, I'm a big fan of reviving old technology. I have a great many elderly relatives and customers who are comfortable with their hardware and wish to keep it functional. Good part is, I get paid and the customers keeps coming back.
I truly love component level repair.

[loopyloo]

[QUOTE=TVguy;722069]

This is the viewfinder CRT circuit.
With 5volts connected at P701 :
150mV at the heater pins 2 and 3 (H&HK)

...What is the purpose of this diode in this circuit ? Can I remove it then power up to see if it was pulling the circuit down ?

Clearly the horizontal scanning circuit is not functional. D702 cannot be removed with the circuit energised.
It is the efficiency diode responsible for the first half of horizontal scanning. In conjunction with flyback tuning capacitor C714, it clamps the negative excursion of the resonant circuit and gradually discharges the energy stored in the bulk inductance of the scan coils and FBT to allow the magnetic field to decay at a predetermined rate; thus completing phase four of four sequence scanning. Removing it will certainly be destructive as the resonant oscillations will not be damped.
Sadly, in true Pana style the circuit has been drawn incorrectly (note that it shows the vertical oscillator driving the horizontal output on pin 22???).
Look at the scan coupling capacitor C712 and horizontal drive dump capacitor C711. The horizontal output transistor Q702 needs a decent base current to get it inspired to amplify. If the electrolytic capacitors are small can aluminium types, they will have gone to God.
Forget active testing and check all electros with an ESR meter. This is a labour of love and you need to make haste slowly.

The small video drum on these units used four video heads to achieve a full frame scan. The image you have presented would indicate either complete head wear failure, or more likely LV power supply issues. Those horrid can electros had a tendency to fail in an unenergised state. Recapping these is not for the faint-hearted, as the electrolyte can leak and damage PCB traces and vias.

BTW, I'm a big fan of reviving old technology. I have a great many elderly relatives and customers who are comfortable with their hardware and wish to keep it functional. Good part is, I get paid and the customers keeps coming back.
I truly love component level repair.

I certainly suspected that caps would likely be at least part of the problems.
I can't see any cap leakage anywhere, which just makes fault finding even harder.
Considering it contains around 1,000,000 aluminium caps, pulling it apart, change a cap, putting back together to test, add 50cents, Pull it apart again......and so on .... I think I will just bin it.
I would have been prepared to put the time in to replace them but not the possible huge cost.
I also thought it would be good if I could adapt the lens unit to fit my Pentax camera since it is a cine lens, but that also doesn't look too easy to do.
Shame really.

Thanks heaps guys.

[tristen]

Loopy, buy yourself a capacitance/ESR meter on eBay.

I bought one as it was only a few dollars in value and was recommended by another member in this section of the forum a year or so ago.

It works well.

It was something like the one listed at .

[loopyloo]

Loopy, buy yourself a capacitance/ESR meter on eBay.

I bought one as it was only a few dollars in value and was recommended by another member in this section of the forum a year or so ago.

It works well.

It was something like the one listed at .

Yeah I own one of these :

[tristen]

Yeah I own one of these :

Good.

In that case you have the means to test the electros in the camera.

Remove, test and replace only those those that are faulty.

...I would have been prepared to put the time in to replace them but not the possible huge cost

Yes, I know that it can still be an expensive exercise in time, but it will not be as expensive ($$$) as replacing every electrolytic capacitor.

If you have the time and the inclination go ahead. If not, abandon the project (although it is likely to keep you awake at night wondering....).

[TVguy]

[QUOTE=loopyloo;722111]

...Considering it contains around 1,000,000 aluminium caps, pulling it apart, change a cap, putting back together to test, add 50cents, Pull it apart again......and so on .... I think I will just bin it...Shame really.

Thanks heaps guys.

Don't give up yet. Two caps on the EVF are hardly difficult to replace. I just use normal radial electros in parallel to check if it will spring into life.
As far as recapping the 10^6 caps goes, that is not necessary.
As Tristen suggested, get an ESR meter. The K2574 Silicon Chip ESR meter kit I built about a hundred years ago has been the best test tool I've ever had.
You can ring test the FBT in this little EVF by desoldering the part and connecting a square wave audio oscillator at 15,625 Hz to the primary winding. Monitor the secondaries with an oscilloscope and look for clean undamped oscillations.

Lack of colour playback does not point to the video heads (due to the 627 kHz colour under system). Synchronisation is everything in a magnetic tape playback system.
Poor off tape H & V sync, as well as control pulse will lead to PLL loss of lock. Clean the hell out of everything in the tape path with isopropyl alcohol again and again.
Baby steps and some fun along the way.
Focus on the EVF first by piggybacking some regular electros on to the in situ aluminium can devices.
I repaired hundreds of these units back in the day and can't say I recall ever having an EVF fault; that said, it was many years ago!

[loopyloo]

[QUOTE=TVguy;722166]

Don't give up yet. Two caps on the EVF are hardly difficult to replace. I just use normal radial electros in parallel to check if it will spring into life.
As far as recapping the 10^6 caps goes, that is not necessary.
As Tristen suggested, get an ESR meter. The K2574 Silicon Chip ESR meter kit I built about a hundred years ago has been the best test tool I've ever had.
You can ring test the FBT in this little EVF by desoldering the part and connecting a square wave audio oscillator at 15,625 Hz to the primary winding. Monitor the secondaries with an oscilloscope and look for clean undamped oscillations.

Lack of colour playback does not point to the video heads (due to the 627 kHz colour under system). Synchronisation is everything in a magnetic tape playback system.
Poor off tape H & V sync, as well as control pulse will lead to PLL loss of lock. Clean the hell out of everything in the tape path with isopropyl alcohol again and again.
Baby steps and some fun along the way.
Focus on the EVF first by piggybacking some regular electros on to the in situ aluminium can devices.
I repaired hundreds of these units back in the day and can't say I recall ever having an EVF fault; that said, it was many years ago!

Ok ok ya talked me into it.
I know the first thing I need to do is figure out how to get to the belts. If I clean them with alcohol will put the grip back into them.
I can only see one behind the battery housing but the schematic shows two. I think I will need the camera all connected and running to properly check the EVF.

I'm in the middle of building my jukebox at the moment so will post more on this camcorder as I get to it.
Worse part is if I leave this one too long I will forget how to put it back together and in particular which screw goes where. lol