KMD GS159SD

[52 Bill]

KMD GS 150 SD
Anyone have a schematic for one of these? I mainly need the power amp section.

Two darlington outputs with a few burned beyond recognition resistors.

Looks like this was made by Yorkville maybe they have one.

[Enzo]

Bill, is that a KMD159 or is it really a KMD150?

My file shows I have KMD150SD. Exactly where that folder might be is a good question.

If Yorkville made these for Kama, I wasn't aware of it.


KMD was a brand of Kaman, which used to be a distributor of music stuff. (straps, stands, etc.) Fender bought them a while back but sold them a couple years ago. Kaman, and by extension ( I believe) KMD, is now part of JAM industries. US Music corp.

You might contact them, it may be faster than me finding mine.

[g1]

Yorkville did occasionally do contract builds for other companies, if it has their name on the board or something.
I believe they also built some GK cabs.

[52 Bill]

Sorry, KMD GS 150 SD.

The back of the amp is marked made in Canada and everything on the board looks just like most Traynor/Yorkville stuff from the '80s or '90s. Even the power transformer looks the same. What made me think Yorkville was the output darlington, a BDV67D. I actually have one in the drawer of Yorkville parts.

Thanks for the info.

[g1]

Oh my. What a debacle that BDV66/67 thing turned out to be for them. (I think it was the 66 that gave all the issues)
Supposedly Philips changed the spec and everything went sideways for Yorkville. There was a nasty update for the Bloc250B(?) that involved retrofitting and extra pair of outputs.
Perhaps this KMD is similar to the Bloc150 ?

[Enzo]

Just sub TIP142/147 for that pair. it works fine, and MArshall even did that in production.

[g1]

Sorry to nit pick but the Marshall sub was for BDV64 and 65.
I got a little off track talking about the whole line of Yorkville products that were designed around the original BDV66 & 67. Something about them was changed by Philips and the replacements had high failures. They tried using MJH11017 & 18 which were higher spec than the Tip142 and 147 but even the MJH's would not hold up. Perhaps it was just a poor design and they were pushing them too hard. If memory serves it may have been some kind of oscillation issue.
Anyway, if I see BDV66 & 67 in a higher power setting I get worried. I'm not aware of anyone other than Yorkville ever using that pair.
Perhaps the Tip142 and 147 will be fine in this application, but it is supposed to put out 150W, are a pair of them reliable for that?

[J M Fahey]

If well dissipated, a single pair of TIP142/147 is good for 100W/4r , I use exactly that, with +/-40V rails and a low drop transformer and have no problems whatsoever.
Anything higher simply goes beyond max safe voltage or max current, period.

Can somebody post/link Yorkville Bloc150/250? all I have is 50 which is fine, well within specs.

[Enzo]

Sorry, I leaped without looking. hey...I'm old...

But back to the issue.

The TIP142 is rated at 125W, So is the BDV66. The TIP142 is rated at 10A continuous, the BDV part at 16A. But I'd think a 10A part would be enough?

If instability is making them shake themselves apart, ther ought to be a fix.

[J M Fahey]

If load is 4 ohm and rails are +/-40V , that means *exactly* 10A peak and not one iota more.

Real World speakers can dip below nominal 4 ohm, of course, downn to 3.2 or 3.4 ohm at certain frequencies (usually between 200 and 400 Hz) but since supply also drops from unloaded 40V to something around 32V , it still holds.