STK404-140S Question

[J M Fahey]

Worth asking.
Amp is made in China, but they should have a small stock of parts in USA for warranty repairs.
I also found suppliers offering the 140-N version, made by ON , which is more likely to be true, than unavailable for years Sanyo. (140-S)
All are pin compatible.

Pity Mouser/Digikey/Futurlec which presumably can be trusted, show "out of stock".

JPBass had kindly uploaded this schematic: http://music-electronics-forum.com/a...ustic-b200.zip

[MarkusBass]

What is funny is that I can buy STK404-140S in Poland for about $15. But, taking into account my latest adventures with fake 2SC5200 transistors, I wouldn't trust that they are original.
Here is a schematic of the module but at first glance it does not match your board.


You can always try to buy it from OnSemi: http://www.onsemi.com/PowerSolutions...=STK404-140N-E

Mark

[Jazz P Bass]

The On Semi 140N-E works as a replacement.

[The Dude]

The manufacturer no longer supports this amp. In fact, from what I can glean from several web searches, because of IC failures and part availability, they redesigned the amp with an output section built from discreet components and called it the Mark II. All of this is unverified. I'm currently investigating the prospect of getting a Mark II power supply/output module for the amp (if what I read is indeed true). I'm aware that the On Semi 140N-E would work as well, but those are also apparently discontinued and it'd be a crap shoot as to whether you are getting fakes or not if you could find them.

[J M Fahey]

Try to get that.
If impossible, and you donīt mind getting your hands dirty making a small laser transfer PCB, I can send you the design of a simple general purpose one I use for "unrepairables".
Fed and cooled by original supply and heatsink.
Just how much free space do you have between PCB and top edge of heatsink?
You will probably have to redrill it to accomodate a pair TO247 transistors, which provide the muscle.

[The Dude]

Thanks for pointing out the schematic link, Juan and thanks JPB for uploading it.
FWIW: The schematic shows the rail voltages at +&-52 for the STK IC and of course the obligatory +&-15 for the op amps. If need be and the customer agrees, I should be able to find a replacement amp module to install. But, I'm first waiting to hear back from Acoustic to see if they have something already built for this chassis and how much they want to soak me for it.

[The Dude]

Try to get that.
If impossible, and you donīt mind getting your hands dirty making a small laser transfer PCB, I can send you the design of a simple general purpose one I use for "unrepairables".
Fed and cooled by original supply and heatsink.
Just how much free space do you have between PCB and top edge of heatsink?
You will probably have to redrill it to accomodate a pair TO247 transistors, which provide the muscle.

There is about 2 inches from PCB to top of heatsink. If I can't get something from Acoustic, I may well take you up on your design. I don't mind getting my hands dirty at all. I'd much rather have the TO247's than trust another STK!

[glebert]

Thanks for pointing out the schematic link, Juan and thanks JPB for uploading it.
FWIW: The schematic shows the rail voltages at +&-52 for the STK IC and of course the obligatory +&-15 for the op amps. If need be and the customer agrees, I should be able to find a replacement amp module to install. But, I'm first waiting to hear back from Acoustic to see if they have something already built for this chassis and how much they want to soak me for it.

There are some class D power amp modules on Ebay for less than $20 that work on 35-55V. Can't be much less reliable than the fake Sanyo parts. I'm thinking of getting one and putting it into a failed Gallien Krueger 400B that is vexing me. I could maybe even use the 500W module....

[nickb]

There are some class D power amp modules on Ebay for less than $20 that work on 35-55V. Can't be much less reliable than the fake Sanyo parts. I'm thinking of getting one and putting it into a failed Gallien Krueger 400B that is vexing me. I could maybe even use the 500W module....

I've bought and used a 100W class D module from that source based on a TDA7492. No complaints from customer do I guess it's still going. Also consider the 100W TDA7293 modules from the same source that will take AC or DC and go for under $4.00 (!!!).

[Jazz P Bass]

Can you link the 'source' for the Class D modules?

[nickb]

Can you link the 'source' for the Class D modules?

only $6.30

2 x 50W TDA7492 D Class High-Power Digital Amplifier Board AMP Board+ Radiator | eBay

You run the outputs bridged to get 100W, although 80W is more realistic expectation IMHO.

[glebert]

If you just search in ebay for "class D module" you will find lots of different options. You can add "mono" or "stereo" depending on what you want. I've seen 500W, 250W mono boards, at 100W and below they seem to go to stereo modules. Supposedly the bigger modules can also be run half-bridge to link two modules for double the power but I don't know that I want to do kW amps with ebay parts just yet.

[The Dude]

Well I just heard back from Acoustic.

"Unfortunately we don't carry any parts for our amps. Typically if we have a customer that is having issues with their amp we just have them replace the whole thing with the retailer they purchased it from since we don't have access to parts that we can get out to technicians."

I'll be having a conversation with the customer to see how he wants to proceed.

[J M Fahey]

"Unfortunately we don't carry any parts for our amps. Typically if we have a customer that is having issues with their amp we just have them replace the whole thing with the retailer they purchased it from since we don't have access to parts that we can get out to technicians."

Meaning: "we have no clue, we didnīt even design it, canīt even read a schematic. Weīre just a bunch of [insert University name here] Business School graduates who created a new Company, bought Acoustic name because it was available and reasonably priced, got a few investors and found this wonderful Chinese Company which takes care of the dirty details"
Disclaimer:
"Any similarity to living or dead persons is not a coincidence"
Oh well

[The Dude]

Any comments on this?

IRS2092 CLASS D Audio Receiver Power Amplifier AMP Kit 200W MONO Assembled Board | eBay

It will fit physically. Reviews that I can find seem good. Specs seem like it will work with my existing supply. Price is right. I'm just a bit leery of more fake Chinese crap. I'm wondering if anyone has tried such things and if so what the results were.

Juan,
I've also PM'd you in regards to post #20.