Amplifone B+ missing

jehuie

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Trying to fix this Star Wars monitor. Have replaced all the caps and the 4 transistors on the heat sinks but the game is missing the B+. Not getting any reading at all.

It has the beige Cinelabs flyback and it looks to me like the only thing in the circuit besides the flyback is a diode (not sure what size it is) which I think is ok. I pulled one end and tested it and no current gets through one way and the diode setting reads 1.5 the other way on my meter.

So my question is, does this mean the flyback is shot? I've heard that the Cinelabs ones were pretty bullet proof. Thanks!
 
Oh, and by the way, I did follow the manual directions for setting the HV except that I don't have an HV probe so I was watching the B+ to see if it jumped. Is this a valid way to do it or must I have an HV probe? In any case, the B+ never got any reading at all.

So I'm not sure if it's a bad flyback...or could it possibly be something wrong with the overprotection circuit?
 
well I've been seeing star wars uprights going for $125 lately, so I can come pick that one up and get that headache off of your hands if you'd like. :)
 
It could be a million things. Do you have proper voltages coming out of the deflection board? are the regulators on the HV board working ? Do you have an open jumper ? is the BU406D good ? Is your over voltage protection circuit shutting it down ? Do you have a good ground to the dag spring ? broken harness wire somewhere ?

Those are just the things i can think of without giving it a whole lot of thought.

You need to read the Amp Faq , order a bunch of parts and have at it. If you try and troubleshoot the one thing that is wrong, you will probably be right back here with a new problem in no time.
 
Ok I'm purchasing some parts....one question. The BU406D cross references as part number NTE379 which I think Fry's Electronics carries. However, BU406 cross references to the same thing and the Amp FAQ says not to use BU406....do you know if the NTE379 is ok then? Or should I steer clear of it and try to find an actual BU406D somewhere?
 
BU406 and BU406D are not the same thing... you need the 'D' as it indicates internal protection diode.

Right. I gathered that. However, the NTE cross reference for both give the same number. That's why I was asking. I'm thinking the 'D' one can be used in place of the non-'D' on and that the NTE can be used for both. At least I hope so.
 
most horizontal output transistors have a diode across them - either internally such as your BU406D or exterbally using a separate component.

I have often used any old output transistor and whacked a high voltage - fast diode across its legs for good measure - works well.
 
most horizontal output transistors have a diode across them - either internally such as your BU406D or exterbally using a separate component.

I have often used any old output transistor and whacked a high voltage - fast diode across its legs for good measure - works well.

Can I do that in this case? I don't think this new transistor is correct (NTE379). Here's what the Amplifone FAQ says is correct readings along with what I actually get:

· Base to collector = Junction drop (between 0.470 and 0.690v) - I get 0.560

· Base to emitter = reads a short, or about 0.020v (YES, A SHORT. This is correct, remember the internal dampening diode and resistor??)
- I get .574 (this isn't right is it)

· Collector to base = Infinity or open circuit (I get infinity)

· Collector to emitter = Infinity (I get infinity)

· Emitter to collector = Junction drop (but I get infinity)

· Emitter to base = Short (but I get .574)

I am very tempted to put it in and try it but I read that it can do damage if it's not right. :(
 
No answer on this one huh? Well to be safe I'm not installing it. Anyone have a suggestion on where to pick up a BU406D then as well as the other main Amp parts? Does anyone make a kit for this?
 
Bob Roberts sells the BU406D...

Well I swapped out the BU406D a few weeks ago and tried it out but I couldn't get HV...the overvoltage light was lit but I didn't have a HV probe and then I got sidetracked with other things and had to put it away for a while.

Anyway, tonight I got a HV probe and decided to try again. I followed the directions in the Amp guide but could never get anything so I started putting stuff away but just as I started to give up I suddenly heard the crackle of HV and the neck started glowing. I had already removed the HV probe so I don't know what the reading was but I looked at the front and I had a picture! But it was way bright so I quickly turned the game off so that I could adjust that down. But then when I turned it back on, there was no HV again and no amount of adjusting would bring it back. Hmmmmmm.

What was that movie where the catatonic people came back to life temporarily and then went back into their stupor? This was the same kind of feeling kinda. :(
 
Well I swapped out the BU406D a few weeks ago and tried it out but I couldn't get HV...the overvoltage light was lit but I didn't have a HV probe and then I got sidetracked with other things and had to put it away for a while.

Anyway, tonight I got a HV probe and decided to try again. I followed the directions in the Amp guide but could never get anything so I started putting stuff away but just as I started to give up I suddenly heard the crackle of HV and the neck started glowing. I had already removed the HV probe so I don't know what the reading was but I looked at the front and I had a picture! But it was way bright so I quickly turned the game off so that I could adjust that down. But then when I turned it back on, there was no HV again and no amount of adjusting would bring it back. Hmmmmmm.

What was that movie where the catatonic people came back to life temporarily and then went back into their stupor? This was the same kind of feeling kinda. :(

Awakenings :)

Found a supplier in Australia
http://www.rockby.com.au/searchres.cfm?select=23&subcode=116&offset=1011&stock_no=20347

Andy's arcade had the kits, but has not got any in stock at the moment
http://www.andys-arcade.net/store/index.php?act=viewProd&productId=517

A list of parts from Andys kit is here
Amplifone_HV_Rebuild_list.jpg


Secondly, If your board worked for a while then it's possible it's just a setting

The FAQ says you need to set the HV and freq pots to the middle of their respective setting. Try that

Once the HV light comes on it will not reset until you remove power and turn on again
 
The FAQ says you need to set the HV and freq pots to the middle of their respective setting. Try that

Once the HV light comes on it will not reset until you remove power and turn on again

Thanks for the info. And yeah I did follow what the faq said. I tried both ways actually...from the manual and the faq. But I could never get it to do it again. But then the first time it came to life it seemed fairly random too. It wasn't while I was following the directions. And I did remove power and turn it on again. But the overvoltage light was on again at that point and I could not get it to come to life again.

Yep....Awakenings!
 
Ok latest update:

I had replaced BU406D and had the "awakenings" moment where the adjusting the HV board caused the monitor to start working but after powering it off and back on I could never get it to do it again.

So I went ahead and replaced the additional components I had available for the HV board, these being the MPSU07 at Q2, the 2N3904's at Q1 and Q5 and VR1 and VR2 transistors. I had already done all the caps as well.

I went and hooked it all up, checked it over, powered it up and....it immediately blew F4 on the deflection board. Aaaaaarrggh. What did I screw up now?
 
I might have figured out the problem. I pulled the board and checked the transistors that I just put in to be sure I didn't have any solder bridges or anything but VR2 didn't seem to be reading correctly.

So I pulled out the screw that holds it to the big heat sink and now I get better readings. So my question is....how do I screw it to the chassis without making contact through the screw? I have the little insulator in there but the screw was making contact....wait a minute....

I think I remember there being a little plastic round insulator in there now that I think about it....let me go look. Hopefully I didn't fry something bad!
 
Yes! I now have Star Wars displaying on my Amplifone. Thanks guys! There's still issues that I need to work through but this is definite progress.

Now the display is all squished onto the bottom half of the screen and it's quite fuzzy. I'll get pics a little later if I can't figure it out.
 
Ok I'm purchasing some parts....one question. The BU406D cross references as part number NTE379 which I think Fry's Electronics carries. However, BU406 cross references to the same thing and the Amp FAQ says not to use BU406....do you know if the NTE379 is ok then? Or should I steer clear of it and try to find an actual BU406D somewhere?

Another place for future reference is
http://www.andys-arcade.net/store/index.php?act=viewCat&catId=92
 
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