Panasonic AG-7500A: Can't load tape

[ESigma25]

I acquired a Panasonic AG-7500A S-VHS VTR off eBay recently, and it has a problem I don't really understand. When you power the machine on, the head drum starts spinning on its own and none of the transport buttons on the front panel do anything. You also cannot load a tape, and if you load one manually the machine will not thread it or eject it, it has to be ejected manually by operating the loading mechanism in reverse.

Here's a picture showing the head drum spinning:

https://i.imgur.com/84C2gkR.jpg

Where do I even start with this? I have a service manual, thankfully, but I don't even know what's causing this problem.

[MIPS]

All bets are off until it is entirely recapped.

[redk9258]

Mode switch?

[ESigma25]

Originally Posted by redk9258

Mode switch?

That could be it. Unfortunately for me the mode switch on this VCR is *weird* and seemingly can't be disassembled, so I guess to clean it internally I'd have to submerge it in isopropyl alcohol.

[ARC Tech-109]

I have a Panasonic AG-7500 and used the PAL service manual pdf on the'net to rework the power supply, same goofy issues. Issue is the supply is actually a DC buck design and uses these oddball switching transistors, currently it still has a 120hz ripple that's superimposed on the HF regulator and its getting into the chroma upconversion stages...

I've had the deck since new and mechanically it's been solid, the bonus was the independent audio channels and I used a Sanyo N55plus on the linear side. If I had to bitch it would be the brittle plastic parts for the flip down control drawer and now the electrolytics, Panasonic got carried away with them.

Best advice I can offer is to pull out the rear power supply board and replace all the caps with low ESR equivalents where possible, do a Google search for the Panasonic AG-7500P service manual pdf or grab the CD Rom from eBay, it's item #264941926972 and only $19.25+shipping. They are good decks that are worth the money and effort to preserve, JVC can't touch them.

Didn't see you had a manual.

Mode switch can be cleaned but it's going to take some effort, manually cycle it many times and it will eventually break thru the tarnish on the contacts.
Check the supply voltages and follow the troubleshooting flowchart, again you're going to run into rotten caps that may be pulling down the+5v rails on the logics.

[ESigma25]

Originally Posted by ARC Tech-109

I have a Panasonic AG-7500 and used the PAL service manual pdf on the'net to rework the power supply, same goofy issues. Issue is the supply is actually a DC buck design and uses these oddball switching transistors, currently it still has a 120hz ripple that's superimposed on the HF regulator and its getting into the chroma upconversion stages...

I've had the deck since new and mechanically it's been solid, the bonus was the independent audio channels and I used a Sanyo N55plus on the linear side. If I had to bitch it would be the brittle plastic parts for the flip down control drawer and now the electrolytics, Panasonic got carried away with them.

Best advice I can offer is to pull out the rear power supply board and replace all the caps with low ESR equivalents where possible, do a Google search for the Panasonic AG-7500P service manual pdf or grab the CD Rom from eBay, it's item #264941926972 and only $19.25+shipping. They are good decks that are worth the money and effort to preserve, JVC can't touch them.

Didn't see you had a manual.

Mode switch can be cleaned but it's going to take some effort, manually cycle it many times and it will eventually break thru the tarnish on the contacts.
Check the supply voltages and follow the troubleshooting flowchart, again you're going to run into rotten caps that may be pulling down the+5v rails on the logics.

That power supply area frightens me, I've never seen a piece of gear with FOUR fuses in parallel before...

I have the equipment for replacing caps but I don't own an ESR tester, so I guess I'll have to find bad ones via voltage probing. At least I have a manual!

[ESigma25]

Small update, I managed to stop the head drum from constantly rotating. The front panel controls are still unresponsive but at least now the head drum motor isn't wearing itself out doing nothing.

[djski]

I worked on many AG7500'S and 7500A's. Very dependable unit. The only capacitor issues were on that back power supply board. I don't have my notes anymore but there was a small electrolytic cap on that board which was the cause for the symptoms you describe. There are many labeled testpoints you can hang a probe, I would bet you will see a supply voltage way down and can narrow things down. You can remove the screws securing the entire back panel and the wiring will allow you to pull it away from the chassis so you can easily access ares on the P.S. board.

You don't need to worry about that cylinder motor spinning needlessly, it is very rugged. The mode switch is also very dependable. You can easily remove it but clean it with tuner cleaner or contact cleaner which is safe for plastic and work it back and forth.. Alcohol won't cut it.

[ESigma25]

Originally Posted by djski

I worked on many AG7500'S and 7500A's. Very dependable unit. The only capacitor issues were on that back power supply board. I don't have my notes anymore but there was a small electrolytic cap on that board which was the cause for the symptoms you describe. There are many labeled testpoints you can hang a probe, I would bet you will see a supply voltage way down and can narrow things down. You can remove the screws securing the entire back panel and the wiring will allow you to pull it away from the chassis so you can easily access ares on the P.S. board.

You don't need to worry about that cylinder motor spinning needlessly, it is very rugged. The mode switch is also very dependable. You can easily remove it but clean it with tuner cleaner or contact cleaner which is safe for plastic and work it back and forth.. Alcohol won't cut it.

Good to know, I'll focus my attention on that power supply board then.