Power supply takes out YM2149

[JoeFloyd]

Hi,

I have a US STFM with a dead power supply. I've been using a 12/5v power supply that is intended to be used with external hard disk drives and this has been working well, but I wanted to return the STFM back to a more original state. I ordered a used/tested power supply from an on-line vendor that specializes in Atari hardware for about $40. Today I installed this supply and upon flipping the power switch I heard a clicking sound coming from the direction of the power supply. A few seconds later smoke came from under the Atari disk drive. I quickly turned off power.

Upon disassembly, it turns out the magic smoke came from the YM2149 sound chip. There is now a nice hole in the top of the chip to help with cooling. I removed the now destroyed chip and installed a 40 pin socket along with a new YM2149 that I have on hand. Using the 12/5v hard drive power supply the machine once again boots up and appears no worse for the wear.

I then started to look at the "new" power supply, this time outside of the computer on the bench. After applying power to test output voltage a cap exploded in the low voltage DC side of the power supply. For sure a bad power supply.

Not sure exactly what voltage the power supply put out when first installed, but my guess is that some AC was present on the DC rails. I've contacted the vendor to see if there is something they might be willing to do, but my guess is that a used/tested supply is a buyer beware kind of situation.

I think I'm going to avoid vintage Atari power supplies as a drop in replacement and just use the supply from of the external hard disk drive. You can buy these hard disk supplies for $5 on ebay. I'll take the power brick apart an pull out the PCB. I can then mount this PCB on the Atari sub-frame. So, then I can keep the Atari power plug and switch which will keep the machine looking 100% original on the outside while using a more reliable modern power supply internally.

[exxos]

Odd.. Where did you get this supply from ? Was the caps changed or even in backwards ?

For not much more you could have got a new PSU from the store.

[rubber_jonnie]

My advice would be get a Meanwell RD-50A. They are very inexpensive (under £20 excluding delivery) and you can still fit them to the Atari PSU subframe and retain the switch/IEC socket and allow for an external look that stays faithful to Atari.

This is one in my Mega 4:

Meanwell_Mega4.jpg (105.21 KiB) Viewed 2600 times

I know folks have also used these in STFMs too.

[JoeFloyd]

Odd.. Where did you get this supply from ? Was the caps changed or even in backwards ?

For not much more you could have got a new PSU from the store.

I purchased the used supply from The Brewing Academy. The Brewing Academy sells vintage Atari hardware and modern upgrades. From what I understand the vintage Atari machines are normally found as part of school surplus auctions and resold at reasonable prices. ~$90 for an untested STFm (+$40) shipping, which is still less than most private sells.

I've placed several orders from The Brewing Academy and haven't had any issues until this vintage supply decided to cause problems.

Also, I'm on the H5 pre-order thread and placed an order for an H5 board via the webstore a couple weeks ago.

Does the H5 have the same mounting points for the OEM power supply?

Thanks,

[exxos]

never heard of them...

Yeah the H5 is designed to all fit in a original case with PSU.

[mikro]

I'd be very surprised if they recapped anything for such prices. I guess they just take the gear, clean it up and resell. Cheaper is not always better.

[chue]

If you are going the Meanwell route, also consider the RPD-60A.

https://www.digikey.com/en/products/det ... 0A/7706011

I have this in my STE/STF.

04647F8C-3B00-45B9-9B42-24D2BDFA911C.jpeg (673.98 KiB) Viewed 2512 times