The elusive YD1022...

[Chevboy0167]

Thanks for looking TheRP. Crap deal for sure. I have like 6 NOS 7222 Toshiba's sitting here... and even a few used. May try an ebay 18 Ultra WX ST for my first course of action if nobody has any other leads..... poop!

 

[sunbulls]

After doing a little study I found several TA7222APcomponent variations between the slightly different Cobra 25 models, not only the 25LTD in question, but also the GTL and sound tracker versions. I stopped looking at the 29LTD YD1022 vs. the 29LTD TA7222AP info and schematics entirely. It started to get way too confusing, mainly because the part numbers and layout is a little different than a 25LTD. I’m only focusing on two things at this point, the print side of the YD1022 board and the schematic of a TA7222AP 25LTD. I can easily see there’s more to it than just changing around components and values. Some circuit traces need to be cut near the chip and rerouted. Others may approach it differently. I would start by removing the YD1022 and all associated components that surround it. Mount the TA722AP and a continuity check afterwards to make sure the heat sink portion isn’t making contact with the chassis. I would then focus on one pin at a time starting from the chip end, but also consider that same pins final destination. All the components and connections associated with that pin in accordance with the schematic should be mounted between those two points within the shortest possible distance. I’m not concerned about following board part number locations. The print side traces will need to be somewhat changed anyway. In other words be prepared to also make small jumpers and print cuts in a few places. Pins 3, 7, 8 are grounded and pin 2 is not connected to anything in the 25LTD TA7222AP version, so at least that will make the transition a little easier.

I also noticed another common component that's often associated with this chip. A .01 bypass capacitor is placed between the chips heat sink and chassis ground (not common board ground). For that you will need a small ring terminal with a star washer placed behind the chips mounting nut. Chassis connections are a pain unless you have a gun or a high wattage iron. You may get by without this cap, but its purpose is to solve possible squealing issues.

 

[Chevboy0167]

Thank you sunbulls. May try this route if I strike out on a pull from an 18 Ultra. I am willing to sacrifice 20 bucks or hopefully less for a used IC just for ease of installation. My 25 had a bad 1000uF cap in the audio chain. Now she has all new Nichicon 35V upgrades. Stay tuned!

 

[Handy Andy]

Well when you look at the schematic of the 25's version - no wonder people abandoned them in droves...

Not too often to you see a schematic DRAWN in showing Pin 3 as the NFB UPSIDE down as if it referred to the "process Triangle" as if it was a power feed.

So I know he's in for a lot of fun. Even the silkscreen used to show the part location using a different KEPC board, again, no parts are matching up to the schematics' ones very well, so what he'll have to do is; not just re-label the parts but integrate the TA7222AP into this pin package by cutting Pin 10, Pin 9 from each other, Pin 7 and 8 from each other - and Pins 5 and 6 from each other and then rebuild and extrapolate from that...

Might be easier to use the TDA2003 - but I went there before and never heard back so...