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Thread: Wei-Ya CGA monitor chassis 429H & 429W

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    Wei-Ya CGA monitor chassis 429H & 429W

    Ok. where do i start with this, well i have been a member of many international forums for some years & only new here, after a friend suggested i should join & share my knowledge, so i hope this will be the first of many threads..

    Here in this i would like to shed some light on the little known Wei-Ya 429H monitor chassis, starting with it's Origins / Heritage, then the Pit Fall's / what to look out for when buying & things that should be Up-graded & Modification.. P.S. you need to have a tube or donor TV with a CR23 neck plug as common with most arcade monitors.

    I know many people will have doubts about these chassis as one would expect & i hope to set your mind at ease, starting with the standard 429H chassis as bought direct from China, there is several different types of this same model number & some have degauss with others not fitted, then many different PCB types, where as the 429W version has been "re-manufactured" & selected from many of the available types for best modification purposes. But these all seem to have a common ground.
    Wei-Ya have a very strong back ground that dates back to the early 90's in many different forms / types / model numbers & much of the design is almost a direct copy of many well known chassis of the 80's, the early We-Ya chassis are known as 825H & 826H with this 429H being a half cast between both of them.
    So let me fill in some details of history & this system, to start with the DC power rectifier system can date back to early 70's in the Well's Gardner 19V1001 & the same as Motorola 501-10 both B&W monitors, then into the 80's was used on many more color chassis, it is very simple with a diode bridge large filter capacitor & then big transistor with a bypass resistor over it. Now we have some DC we can look at the system, the RGB comes in via a 47uf cap' then set of 2Sc1815 (the same transistors as WG 19K4900 chassis) there are many alternatives for this transistor, from here the RGB go's to the neck PCB to another very common design with only a single 2SC2688 transistor with high gain to drive the tube (again there are many substitutes for this transistor) so in short the RGB go's in & through a few transistors much like every other chassis, very simple.
    The Horizontal & Vertical again is much as of the big monitor manufactures back in the 80's were they have used the Hitachi HA11235 chip with components & capacitors as recommended by Hitachi to do the job, as one would expect this being a tryed & tested system, it works ! As for the Vertical on these 429H chassis they have used a Sanyo LA7830 chip to simplify things with less components & have been used in thousands of TV's, so as our tubes are typically old repurposed TV's it will make for easy modification to suit a wide range of tubes/yokes from 23" thru 33" (explained later) but the 429H from the factory is only good for 26" thru 29" tubes with a narrow ohm range, with the Vert' stated ohms of 9.6 will run from 7.3 thru 11.9 & the Horiz' ohms of 1.3ohm is a little tighter but will be happy between 1.1 thru 1.9 ohms. The tube size stated for these seems to be from one extreme to another and does not work for all as the ohms of your yoke will change the aspect ratio of what the standard chassis will cope with.

    Pit-Falls & what to look out for when buying.
    A few years ago i was repairing & re-cap'ing monitor chassis for a local arcade after the owner had seen some of my work in my personal stash of 80's machines & the high quality capacitors used, when they asked me to track down / research the best universal chassis to suit 23" thru 29" tubes so they could have a standard type that is easy to modify, after months of looking i found that suppliers in China have no idea & when you buy, they then go to a warehouse to get your order ( a bit "luck dip") as to what you will receive, so many suppliers have 2 or 3 types in their photo's on the web site to cover them as to what they supply. As these have been made for years & production dates can make a difference with also to mix it up it looks like there have been many different manufactures using the same model numbers with different production PCB's / components . Yep, very confusing.
    So what do you look for ? There is about 4 different builds/types of these & cost/value is a big factor as to what you get, so if you can ask supplier to show photo of the unit you will receive, look for the degauss ( little black box ) near the input main voltage & DC bridge, some will have holes drilled with others missing from the PCB design, it will be best to find one with the degauss (MZ73xRM270V) if you have the holes drilled & it is missing then you can salvage one from you donor TV you have found or you can find then on the net, but there are a few models of these black box MZ739RM270V = 9ohm & MZ7318RM270V = 18ohm, so what does this mean ? well it comes down to the ohm's of you Degauss coil, most will have around 30ohm's but if your coil is lower i would recommend using the 18ohm Black box version. From my research it seems the cheaper versions of these Chassis omit these completely with No place on the PCB to even fit/install one.
    Next it seems some will have heat sinks fitted to the Horiz' out-put transistors near the EHT some will not (note, this missing is not a bad sign, as you can fit one)
    Known problems with every version of these is the large white By-pass resistor across the DC transistor, with reports across the inter-net as they fail (more details later) .
    In short i cannot tell you what chassis is best or who to buy them from as what is there one day they have a different one the next, so best to buy from someone that can show the unit you will receive & can answer a few questions you ask.

    From that it brings us to things that should be Up-graded & Modification.
    As just mentioned above with the DC by-pass resistor going bad, so why does this happen ? when it is a system used in so many old school chassis, well quality of this resistor is a big problem, but when you look back at other manufactures that used the same system & even early versions of this Wei-Ya chassis the value in ohms has changed, why i hear you ask & what should it be ? Here is a run-down, Wei-Ya 826H - 160ohm , Wei-Ya 429H - 140ohm , WG 19K4600 - 180ohm , WG 19K4900 - 150ohm , WG K7000 - 220ohm , Orion PBW2022 - 220ohm , Toei KB240162 - 220ohm , Motorola XM-501 - 150ohm , just to name a few, so how do they have so many different values to do the same job, well the current rating of the transistor along with a large heat sink, the Wei-Ya only seems to use the back panel as a heat sink with no extra, so to keep the heat from the transistor they use a lower value resistor @ 140ohm 25w, these get very hot & due to poor production quality, this 25w is not high enough to cope with the heat dissipation hence it fails, so here we should up-grade, i have done this many ways & all work, you can remote mount a 150ohm 50w ally clad resistor or 180ohm 25w ally clad (both work great) or if you can find a 180ohm ceramic 25w as the same type used in these 429H chassis it is a simple replace job, once that's done we now need to mount a heat sink to the transistor to dissipate the extra heat, you can use a larger TO-220 type heat sink between the transistor & rear panel or on the flip side a much larger heat sink, this will dissipate the heat from the now "doing it's job" voltage regulating transistor. This brings us back to the input AC voltage of 110v this should not be any higher than this as our DC voltage is set to 110v DC tested at R331 6K8ohm 3w, if your step-down transformer is higher @ 117v you should consider changing R740 from 2.2ohm to 3.3ohm 5w as used in the WG K4900 chassis. Next problem is the diode bridge set being only 2 Amp & with the fuse also rated as 2 Amp if we have a problem in the system what will fail first ? so these 4 x diodes D801 thru D804 should be upgraded to 3 Amp 1N5408 will do the job, you will need drill out the holes & scratch back the mask the give a larger solder pad. From here we look at the large DC filter capacitor C802 a 470uf @ 200v these i have noted have two problems being one they in some chassis have used second-hand cap's & secondly it seems to be under rated, with reports on the net that they have even exploded, WG & Orion have used 560uf @ 250v so we should do the same, if you can find a 560uf @350v or a higher voltage it will be great.
    Next in line is just after transistor Q801 is C313 of 100uf @ 160v ( i have found these to be as low 47uf @ 160v & high as 150uf @ 160v) & would recommend going to 150uf @ 250v to give more head room.
    Here i should give a short lesson on capacitors, they are not all the same, as some brands/models will have a higher ripple current & rated life, at your local electronics shop you will typically find two models being standard & long life, the standard version is only rated at 2000 hours with their long life being 4000 hours, well this sounds great but 4K is still low life as some of the Japanese manufactures having 10,000 hours rated life, these are a little harder to find & then there is many different models to select from, so best do some research as to what models are best suited to each part of the circuit, with these Wei-Ya chassis only using cheap Chinese made 2000 hour cap's you need change them all, with most staying at the same values but can go up in voltage.
    Another change that i have made because the original has been known to fail is D401 (10BB4T) this is found about the center of the left side & about 33mm in from the side, this can go either FR154 or FR205, this needs to be a fast recovery diode. Also i would recommend that C401 & C402 be changed from 330uf to 470uf @ 50v.
    As we are in this area i should mention the problems with the heater voltage, from the factory the 429H uses a 1.8ohm 3w this will give you a voltage of aprox' 9.6v AC across the heater, but the recommended voltage for our tube is 6.3v AC , this is resistor R-369 (this is found just up from our ribbon cable to the neck PCB) so now you have found this resistor what do we change it to, well again i can only recommend possible values as each tube will have a different current draw across the heater coil, i have tryed many values & what have i found on the few tubes i ran my tests on & i would recommend these be of the 5w ceramic type, the voltages i found using different value resistors are, 5.6ohm = 7.2v AC, 6.8ohm = 6.7v AC, 7.5ohm = 6.3v AC (note these are aprox' voltages), i settled on 6.8ohm as was a middle of the road value & the 7.5ohm being much harder to find, so this 6.7v AC is much closer to the rated voltage of 6.3v needed than the original 1.8ohm giving 9.6v AC. Please note running the heater at a higher voltage will shorten the life of our tube, so this current limiting resistor must be addressed.

    So you came here to learn how to change the circuit to suit different size & types of tubes, there is only a few components/capacitors that control this part of the system, tube size selection is made via (what is badly marked in the tech' sheet supplied with the China models of 429) Narrow / Wide (Hori. Range) up near the EHT shield & should read "CRT size selection" this is controlled by C909 @ 0.01uf 1.6Kv & C912 @ 0.0047uf 2Kv . with the 0.01uf selected on it's own the chassis will suit 27" & combined these = 0.0147uf and close to suit a 30" tube, the two capacitors are where we will adjust the tube size selection as this is to wide to get good adjustment with the limited range of the potentiometer VR2 or in some older models horizontal coil. i can only give these values that i have used as a rough guide as each tube/yoke will have different characteristics, so these are approximate values, but you should get the idea as to how the system work's to select tube size.
    First i change C912 to 0.0022uf but can go lower to even 0.0015uf or 0.001uf @ 2Kv, this will tighten our tube selection to between only two sizes, now we need select our tube size, here we change C909 _ 0.012uf will give 28" to 30" _ 0.0082uf will give 25" to 27" _ 0.0068uf will give 23" to 25" . again these are approximate values, but we have more ways to trim our tubes sizes, capacitors C908 & C908A are another pair used for adjustments & again the tech' sheet from China is badly marked as (video color) / (ITT) , well it should read H. Width Adjustment (N) lower & (W) high width, from the factory these are C908 = 0.33uf @ 400v and C908A = 0.1uf @ 400v , so the 0.33uf is the larger height & combined they = 0.43uf for bringing size down, how do we use this info ? well changing either or both will reset the range of our adjustments, so if we only look at the 0.33uf and go up in value the size gets smaller but if you go down it gets larger, now if your picture is not out to the full size of your tube or you do not have enough adjustment the either trim/change the 0.33uf down to 0.27uf & vise-versa if your picture is too large change the 0.33uf to 0.39uf or 0.47uf but remember combining C908A will increase sizes to 0.49uf & 0.57uf now if you need to truly trim it more than changing C908A from 0.1uf to the next size either way eg. 0.056uf or 0.12uf will fine tune the H. Width Adjustment.
    Now we may have the problem of Vertical size with not enough adjustment with VR5, this is where buying the better model of these 429H chassis can pay off as some have changed track lay out, with the better chassis using jumpers, the factory 429H PCB is set for a larger size of tube & does not use the inline resistor used back in the 825H or 826H chassis in both these are R426 @ 56ohm's , but on the 429H chassis there is no R426 resistor (Oop's) but it does have a jumper J39 we can remove & select our resistor that will give use a size suited to our tube, so with the 825/6H using 56ohm for a 29" tube it is a good start & the smaller our tube the higher the ohm's we should use up to 270ohm & you may need to try a few values, typically i use 150ohm & this brings us to a big problem of another resistor missing & no pad's to use, so you will need piggy back to other components, when looking at the schematic for the 825H R420 , 826H R370 are both 680ohm & missing on our 429H chassis hence you need install one.
    Another component missing is found on the 826H schematic being C392 22uf @ 50v , again buying a good chassis will have the tracks that can be cut & holes drilled to fit this 22uf cap'.
    So still on the Vertical i will shed some light on the ohm's needed for these chassis to be happy, our factory 9.6ohm is a middle point & we can run between 7.3 to 11.9 this is controlled by the LM7830 chip & current limited via C398 2200uf in the 429H & 1000uf in the 825/6H chassis (why) well the capacitor is used as "current limiting" to protect the LM7830, so if you have a yoke with higher eg. 14ohm's we can let more current through this C398 capacitor by dropping it down a value or two , 1000uf is what i have used with the 14ohm Vert' yoke, so what happens if we have lower ohm's in our Vert' yoke coil, well you will cook the LM7830 chip & you cannot even limit current by going up in value here as the 2200uf is at the top range, so WTF do we do ? Sanyo did us a favor a made a few version of these chips, so for lower ohm's we need a chip capable of a larger current draw, change out IC2 LM7830 to a LM7833, it's that simple & will give us between 5.2ohms & the factory 9.6ohms with a sweet point of 7.8ohms.
    Now the biggest problem of the Horizontal yoke ohms, going higher than the 1.3ohms as on the decal of these 429H chassis is not a problem with heat dissipation but more a picture size, as the higher the ohms the smaller the picture, but we know how to trim this, so higher ohms is Ok to about 2.4ohms, but going lower will heat stress out our transistor Q401 shortening its life, here again buying a good chassis it will have jumpers we can substitute a component, some suppliers will say if you Horiz' ohms are lower than 1.3ohm you can add a 1ohm 5w resistor in the RED lead to the yoke & i can say it works, but why do this when the manufacture gave us a jump J10 & and you can just squeeze the 5w resistor in, but why use a resistor when back in the 90's Wei-Ya was running the 825H down on a yoke with 0.6ohm & this can be found in the schematic as J10 @ 100uH this choke may be very hard to track down without doing a bulk order to get just the one you need for your chassis, hence why many will use the 1ohm 5w resistor in J10..
    The 429W chassis has had these mod's done along with all the capacitors up-graded.
    In short these are a very versatile chassis that can be modified across a wide range of tubes.

    component cross reference :-
    2SC1815 2SC2410 2SC2724 2SC1740
    2SA673 2SA695 2SA1015 2SA950
    2SC2688 2SC2611 2SC2456
    2SD1138 2SC2073
    IC 302 LA7830 LA7833 LA7845
    Last edited by Pac-Invader; 11th June 2019 at 04:55 PM.

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    with all my research i was not able to find a schematic to suit this Wei-Ya 429H chassis
    so i reverse engineered one of the early chassis i re-manufactured to produce a suitable schematic in a PDF
    this helped me do all the workings to do the modifications ..
    but i do not know how to up-load it here for all to use

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    Thank you for this
    This site may be OK for a pdf file
    https://www.keepandshare.com/htm/fil...df_hosting.php

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    Quote Originally Posted by dezbaz View Post
    Thank you for this
    This site may be OK for a pdf file
    https://www.keepandshare.com/htm/fil...df_hosting.php
    Ok.. so i upload my PDF to this site
    then how do i use it here in a post ??

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    Just find the link, and post it here
    Thank you

    - - - Updated - - -

    Just find the link, and post it here
    Thank you

    I just uploaded a file
    The link is at the bottom
    Demo.jpg

    My link is a different chassis
    http://www.keepandshare.com/doc30/vi...id=108790&da=y

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    After i was contacted on another forum about the heater voltage, i have done an edit to the above, to now include details of the resistor that should be changed.

    - - - Updated - - -

    well i found it a little hard to up-load as a PDF & hence converted it to a JPEG
    Attachment 149221

    - - - Updated - - -

    now i have worked out how to up-load pi'c here is a photo of the CR-23 neck board
    Attachment 149222

    and a photo of what i have been doing with the "remote mounted" 25w 160ohm resistor, i used a couple of 6mm long metal "stand off's" from my local electronics shop
    you can also see the large heat sink used behind the voltage regulator transistor
    Attachment 149223

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    Thank you for this effort


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    Quote Originally Posted by dezbaz View Post
    Thank you for this effort

    Cheers..
    feels good to help..
    i have a few of the 429W chassis that i re-manufactured, but i need to pay some fees so i can list in the "for sale" section
    also have a good stock of spare to suit any mod's or repairs on these chassis

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    It's always good to meet a fellow electronics guy on the forums

    I always wondered how it would be cost wise to remake the raster chassis

    I was looking at the WG4900 chassis, as the PCB material is that brittle brown stuff
    I look at the yokes and transformers, and it puts me off
    I think re-using them items nets you a virtually new chassis

    What did you do with these trickier items?

    Pay the fees, i am interested (as I say depending on cost)

    - - - Updated - - -

    Here is a higher res pdf version if guys need it

    http://www.amazingarcading.com.au/We...vader_2019.pdf

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    Sorry to disappoint you as i'm not an "electronics guy" i'm only a Master Electromachanical Engineer

    Cool.. you know how to offer my schematic in a high res' .. thank you .. i have this in a higher res' .. also many versions of each with all my mod's ..

    as for reproducing the PCB's of older chassis, "yes" i have looked & started on the GO-7 chassis
    would be as a replacement PCB / spare part, as i have a few cooked units that need new PCB's

    as a note i have been thinking of trying one of these 429 chassis down to a 19" tube .. & going by my details of tube size selection it should be easy

    "yep" fees.. these days i am retired & live on a pension with limited funds
    Last edited by Pac-Invader; 12th June 2019 at 04:57 PM.

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