No head/drum spin after cold storage...JVC VCR HR-S7600EK

[MyIdenTT]

I have a JVC VCR HR-S7600EK that has been stored for a few weeks in a cold garage. It was all working before storing but now the video head/drum does not spin up. The tape loads and ejects but goes into standby/shutdown when asked to play etc.. Does anyone have any experience with these before I plunge in? Many thanks

symptoms here:

https://www.dropbox.com/sh/xjilg1zpa...BhmO83fda?dl=0

[paulsherwin]

Have you given it time to warm up to room temperature and dry out? The condensation sensor may be tripping.

[IanNVJ35]

That is the model with dynamic drum isn't it? The gear inside the head that drives it cracks and the machine shuts down as improper operation is noted. Note, no spares are available now, you will likely need to replace the head with a non-dynamic equivalent from a similar model.

[Vauxfan2k]

If you have given the machine a few hours to warm up and dry out as suggested then you could try shorting out the dew sensor in case it's duff. Failing that then as Ian says it's needing a new head.

[MyIdenTT]

Hello and many thanks for your replies.

Originally Posted by paulsherwin

Have you given it time to warm up to room temperature and dry out? The condensation sensor may be tripping.

It had at least 12 hours in the house before operating. It was in a cold garage for a few weeks, but inside a 'really useful' plastic box, so hopefully not subjected to too much moisture. It's had two weeks indoors now and still misbehaving..

Whereabouts is the condensation sensor and what does it look like? Is it a circuit protector? It has been suggested i should suspect these - black in colour and about 3-4mm in length and usually designated ICP301, ICP401 or similar on the circuit board but I'm having trouble confidently identifying them - is 'CP' an abbreviated 'ICP' or something different?

Do these have a mode switch -I cannot locate it?

I'm afraid your dealing with the electronically illiterate here. My experience extends to replacing the odd bulgey capacitor. I have a multimeter but am not confident how exactly to test whether the drum is receiving power...

I've managed to find a service manual online. The machine apparently has an 'emergency display function' for diagnostics, but i have not managed to find th 'N' button on the remote to enter ED mode (see earlier Dropbox link).



My apologies for so many questions - I would like to save the VCR if I can - it's a favourite for capturing VHS/VHSC to digital (TBC etc).

[MyIdenTT]

Originally Posted by IanNVJ35

That is the model with dynamic drum isn't it? The gear inside the head that drives it cracks and the machine shuts down as improper operation is noted. Note, no spares are available now, you will likely need to replace the head with a non-dynamic equivalent from a similar model.

It is indeed the model with dynamic drum. If it does come to replacing the drum is there a way of identifying which others - models/part numbers - are compatible?

[John123]

When powered up out of standby, there should be 12v DC present on pin 5 of that drum motor's flat ribbon connector. That's a good place to start! You can easily measure it with a multimeter (negative probe on chassis ground, and positive probe to pin 5).

Just be very careful not to short out any of the pins with the multimeter probe!

[paulsherwin]

If it's had 12 hours at room temperature then it won't be a condensation issue.

[jayceebee]

It's not a machine I've ever encountered but I'm not aware of any JVC domestic machines ever been fitted with dew sensors other then camcorders.

With no tape inserted does the head spin freely if rotated by hand?

John.

[MyIdenTT]

With no tape inserted does the head spin freely if rotated by hand?

Yes, the head does spin freely and moves slightly as the tape is wrapped around it.

[paulsherwin]

Originally Posted by jayceebee

It's not a machine I've ever encountered but I'm not aware of any JVC domestic machines ever been fitted with dew sensors

You may well be right, it was just a guess and I don't know this model personally.

[MyIdenTT]

Originally Posted by John123

When powered up out of standby, there should be 12v DC present on pin 5 of that drum motor's flat ribbon connector. That's a good place to start! You can easily measure it with a multimeter (negative probe on chassis ground, and positive probe to pin 5).

Just be very careful not to short out any of the pins with the multimeter probe!

thanks, John you've found my level

On standby pin furthest from centre of drum has 2.02V. When a tape is loaded or ejected this changes to 1.97V and reverts to 2.02V when the machine puts itself back into standby. At no time does it show 12V. I repeated this test in low light, holding a book over the transport area in case of sensor issues, with the same result.

[IanNVJ35]

Can you hear the dynamic drum motor trying to work?

[John123]

Originally Posted by MyIdenTT

On standby pin furthest from centre of drum has 2.02V. When a tape is loaded or ejected this changes to 1.97V and reverts to 2.02V when the machine puts itself back into standby. At no time does it show 12V. I repeated this test in low light, holding a book over the transport area in case of sensor issues, with the same result.

That could be either one of the FG or PG pulse 'sense' voltages for speed regulation. One of those pins will have the full 12v DC on it to drive the motor, so try the opposite (the pin nearest to the centre of the drum, instead).

There might be a little marking on the PCB to tell you which is pin 1, so easy enough to figure out.

[MyIdenTT]

Originally Posted by IanNVJ35

Can you hear the dynamic drum motor trying to work?

I listened closely to the motor when inserting the tape and could hear nothing from it...

[MyIdenTT]

Originally Posted by John123

That could be either one of the FG or PG pulse 'sense' voltages for speed regulation. One of those pins will have the full 12v DC on it to drive the motor, so try the opposite (the pin nearest to the centre of the drum, instead).

There might be a little marking on the PCB to tell you which is pin 1, so easy enough to figure out.

I found the little mark on the PCB to tell you which is pin 1 and kept the probe on while i inserted the tape:

standby tape in

PIN 1 2.02V 1.97V
2 288mv 288mv
3 139mv 4V
4 -3.7mv -26mv
5 0 5mv

How do you guys tackle this kind of thing? Is there a way of tracing the fault back from the motor to at least to know which board is culprit? I am aware of the forum rules, so have attached only the Service Man table of contents as a starting point...

[MyIdenTT]

have attached only the Service Man table of contents as a starting point...

...and here it is...

[MyIdenTT]

ah ...having trouble retaining my formatting


PIN1 standby 2.02V, tape in 1.97V
PIN2 standby 288mv, tape in 288mv
PIN3 standby 139mv, tape in 4V
PIN4 standby -3.7mv, tape in -26mv
PIN5 standby 0.00V, tape in 5mv

[MyIdenTT]

...on further investigation, it looks like PIN5 at the drum motor ribbon connector arrives at PIN1 of CN3001 on the big board.

This agrees with voltage chart info for CN3001: 11.5V at PIN1. I am not picking up this 11.5V at either end of the cable...where to look next?

[John123]

I think Pin 3 is the 'motor start' (control) voltage, so the drum is being told to start-up, but as the 12 volt supply is missing (Pin 5), it's going into shutdown.

Try unplugging the entire flat ribbon cable and check you have your 12 volts on the opposing connector on the main PCB. If you find it there, then the flat ribbon cable is faulty (try reseating), or there is a dry joint on the connector.

Failing that, the problem is going to be on the main PCB. The 12 volt rail will have to be traced back, and that's a little more involving. Could be an open-circuit resistor or IC protector..or another pesky dry joint (if you're lucky!)

*EDIT* Just saw your latest post, so ignore my middle paragraph. You might also want to check the health of the power supply to make sure a rail isn't missing. If you have the service data anyway, it will tell you what voltages to look for.