Should I be doing preventative maintenance on my BVM?

CrazyDean

Zero's Secretary
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Sep 12, 2016
Posts
155
So, I have had my BVM-20G1U for about a year, and I love the picture that it produces. Everything seems fine, and I've never had it open.

1. Should I open the case and check on capacitors, etc?

2. Is there any periodic servicing that should be done to keep it in good condition?

3. Is there any way to check to see if it's damaged or about to die?

Thanks for the help.
 

Westcb

Give an Azn, A Break Here!,
Joined
May 17, 2012
Posts
1,190
1. No
2. No
3. Not visually most likely, but you could test components I suppose for impedance etc..
seriously just enjoy it while you got it, if you see the picture quality begin to diminish a recap is probably the only thing you could do yourself unless you have experience diagnosing and repairing commercial grade monitors. I would say if the pic is good now then you probably are ok and nothing is about to die.

If the pic quality is bad now I change my answers to Yes :-)
 

SamIAm

n00b
Joined
Dec 4, 2014
Posts
40
I would have to disagree.

There are no traps involved with opening a BVM, at least as far as I have seen. It is literally as simple as taking out screws and removing flat metal panels, much like opening an old PC tower. The worst it got for me was that the back panel had a couple of wires running from the S-video connector to the main unit, and I had to be careful not to yank on them. Unlike consumer sets, BVMs are made to be easily opened for routine maintenance.

In consoles, capacitors often function only to filter signals. These are typically small, they have low-stress lives, and if something goes wrong with one of them, the worst you suffer is crackly sound or some oddity in your picture. In BVMs, however, there are many large, high-voltage capacitors that are directly involved with supplying power. Bear in mind, these TVs easily pull 20 times the wattage that is ever used in, say, a Turbo Duo. The big capacitors are under more stress, and when they fail, you run the risk of both damaging other components and spilling lots of corrosive electrolyte everywhere.

If you have never done it before, I would strongly suggest that you look at the capacitors on the power supply PCB and the deflection card PCB. The former is the one that the power cord connects to and is probably inside of a big metal case, while the latter is a big thing on the left side that electrically sits between all of the signal processing PCBs on the right and the tube itself (not to be confused with the board on top, which is the final RGB signal amp). Combined, there are probably two or three dozen high voltage caps on these. If nothing else, eyeball them for leakage and bulging, both at the top and the bottom of the cap. If any of them are starting to go, I would say to hell with it and replace any cap on the board where the voltage and microfarad ratings add up to more than 100. That, or just replace everything for peace of mind.

If there are no problems, you'll probably be done in 20 minutes, and you should be good to go for hundreds of hours of operation. The risk of damaging your BVM just by opening it is extremely low, while the chances of finding a problem are fairly good, and the advantages of fixing a problem before it becomes a crisis are great.
 
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CrazyDean

Zero's Secretary
Joined
Sep 12, 2016
Posts
155
I would have to disagree.

There are no traps involved with opening a BVM, at least as far as I have seen. It is literally as simple as taking out screws and removing flat metal panels, much like opening an old PC tower. The worst it got for me was that the back panel had a couple of wires running from the S-video connector to the main unit, and I had to be careful not to yank on them. Unlike consumer sets, BVMs are made to be easily opened for routine maintenance.

In consoles, capacitors often function only to filter signals. These are typically small, they have low-stress lives, and if something goes wrong with one of them, the worst you suffer is crackly sound or some oddity in your picture. In BVMs, however, there are many large, high-voltage capacitors that are directly involved with supplying power. Bear in mind, these TVs easily pull 20 times the wattage that is ever used in, say, a Turbo Duo. The big capacitors are under more stress, and when they fail, you run the risk of both damaging other components and spilling lots of corrosive electrolyte everywhere.

If you have never done it before, I would strongly suggest that you look at the capacitors on the power supply PCB and the deflection card PCB. The former is the one that the power cord connects to and is probably inside of a big metal case, while the latter is a big thing on the left side that electrically sits between all of the signal processing PCBs on the right and the tube itself (not to be confused with the board on top, which is the final RGB signal amp). Combined, there are probably two or three dozen high voltage caps on these. If nothing else, eyeball them for leakage and bulging, both at the top and the bottom of the cap. If any of them are starting to go, I would say to hell with it and replace any cap on the board where the voltage and microfarad ratings add up to more than 100. That, or just replace everything for peace of mind.

If there are no problems, you'll probably be done in 20 minutes, and you should be good to go for hundreds of hours of operation. The risk of damaging your BVM just by opening it is extremely low, while the chances of finding a problem are fairly good, and the advantages of fixing a problem before it becomes a crisis are great.

I think I will check it out when I get some time this week. Thanks for the advice. The CRT is beyond my electrical knowledge, so I don't know what I'm looking for. I'll check caps soon, and I hope I can get more than a few hundred hours!
 

CrazyDean

Zero's Secretary
Joined
Sep 12, 2016
Posts
155
UPDATE: I found a service manual online and spent the last two hours inside the BVM. Caps looked good, but I found some pots and decided they needed to be fooled with. Every possible adjustment was painted over. I can only assume this was done to keep the settings from changing during shipping/moving as some of the adjustments were very light and easy to move once the paint was broken.

As for the actual caps, It was difficult to see them through all the bracing inside the unit. From what I could see, they looked good. Sometime in the near future I will pull the actual power supply PCB out an give it a more thorough inspection.

This thing was super dusty inside, too. I'm wondering if I should try to blow it out or just leave it. I wiped off the stuff that I messed with in hopes it wouldn't dislodge and clump up.
 

SamIAm

n00b
Joined
Dec 4, 2014
Posts
40
It never hurts to get a little dust out.

I have yet to see any of the smaller caps in my BVM having ruptured, and I've only caught a couple of the larger ones with swelling at the top. When I have seen quite a lot of in caps of all sizes, however, is bulging at the bottom. It's really worth looking carefully at this area, because it's a subtle thing compared to top-bulging. You have to look for the rubber seal on the bottom sticking out just a little more than it should, or the plastic jacket looking just a bit rounded.

I recommend scrutinizing Elna caps all the more. Those have a bad reputation; one fellow on an MSX forum says that it's company policy where he works to immediately swap any Elna cap. Indeed, the majority of dying caps in my BVM have turned out to be Elnas.

Based on what I've seen in my own manual, it seems like it's only possible to check whether you're adjusting a pot for the better if you've got a multimeter or an oscilloscope on certain prescribed points. There are an awful lot of pots in these, and I imagine that each one affects something very particular that might not be easy to detect with just a couple of on-screen test patterns. I'm sure you were careful, but I would be very sparing with pot adjustments.
 
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