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Space Invaders Transformer Repair

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Purity View Drop Down
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The Oracle

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Topic: Space Invaders Transformer Repair
    Posted: 11 Mar 2018 at 7:58pm
Has anyone found a substitute for the square rectifier block and the big blue cap on a Taito Space invaders transformer?

Im getting 28v on the 9v line so one of these parts are at fault. All other voltages check out ok

Edited by Purity - 12 Mar 2018 at 11:36am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 11:38am
The square block is actually a rectifier.  They are in the manual as:

16LASN-2200 Capacitor
Rectifier 12C20 (A)

The cap should be easy to replace but the rectifier might be a different story :-(
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb lilley Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 11:55am
I read that as 12 Amp, 200V rectifier. Shouldn't be too hard to find on ebay?
It's only original once.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 12:10pm
There are two pins on the 12C20

http://www.ukvac.com/forum/taito-space-invaders-transformer-part_topic358912.html

A 12AMP 200V rectifier would have 4 pins e.g.

https://www.ebay.co.uk/itm/BRIDGE-RECTIFIER-12A-200V-MPN-GBPC1202-E4-51-VISHAY/351144917141?epid=1681855643&hash=item51c1de3895:g:BhEAAOSwFTRTpJDJ

There is a similar one used on a cocktail Space Invaders.  I wonder if it uses the same value?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmurr Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 1:03pm
Can you post a photo of it?  My schematics have a reference to an S4VB rectifiers which seem to still be readily available and cheap

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 1:06pm
The rectifier from the upright is in the link:

http://www.ukvac.com/forum/taito-space-invaders-transformer-part_topic358912.html

The rectifier in the cocktail seems to be a S4VB.  I can take a picture later this evening of the cocktail rectifier


Edited by Purity - 12 Mar 2018 at 1:07pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RaveN Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2018 at 1:09pm

A typical bridge rectifier is just a name given to four diodes in a package, that will do full-wave rectification.
Most early games used the more inefficient half-wave method, meaning more stress on the smoothing cap, which has to be larger to deal with the higher ripple current, as half of the AC wave form wasn't utilised.  Hence why you see such large caps used back then.

For Half-wave, you only need 1 diode (hence the 2 legs you see on the package rather than 4).
12A is too much to put through a discrete diode, hence why they were packaged and bolted/part of a metal bracket.
I would buy a high power diode in a TO case, and screw it to the same metal/heatsink, such as:
https://uk.rs-online.com/web/p/switching-diodes/8292768/
Welcome to bonus stage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tonyg64 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2019 at 8:48pm
Purity, did you find the solution for the rectifier? I may have a prob with mine.

Cheers

Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 10 Nov 2019 at 10:56am
Originally posted by tonyg64 tonyg64 wrote:

Purity, did you find the solution for the rectifier? I may have a prob with mine.

Cheers

Tony


My bridge rectifier was actually ok.  It was just the holder that was broken
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tonyg64 Quote  Post ReplyReply Direct Link To This Post Posted: 10 Nov 2019 at 5:55pm
Ok cheers

Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pinball dunc Quote  Post ReplyReply Direct Link To This Post Posted: 10 Nov 2019 at 9:49pm
hi i am new to this this arcade fixing .but if you try rsonline they might be able to source a similar rectifier. i got a problem with my nichibutsu moon base ( a clone of space invaders)the power supply cooked a cap near to one the transistors .replace the the caps and transistor but i have not been able to sourced a ceramic resistor on the board . it was a 4u 1.5watt  ceramic .would it be ok to use a 4u 2wor is there a way to use 2 resistors to get it to the value of 1.5w. with the 2w 4u the voltage was low .3.56 instead of five volts. any answers would be appreciated .ta
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