9444A

[bfish]

The current-limiting bridge is adjacent to the bias pot, a shorted component in that area could cause such a problem. Having a good channel next door for comparison is sure a plus!

Happy New Year!

[gvasale]

How much difference is there between the 9444 and the 9440A? (not considering the meters)

[bfish]

Simply put, 17.25 pounds, (mostly transformer), not counting the meters.

[gvasale]

thanks, but any chance of a little more detail?

[cclark65]

The 9440A is a completely different beast. It was made in 1974 or somewhere in there, the 9444 was introduced in the late 80's (I think)

I have 9440 service manuals if you want some pdf's, just send me your email address. I'll take them to work...we have a digital copier that does a sweet job of making PDF files and emailing them

[gvasale]

Thanks Charles. I have photo copies of the operating and service manuals. I got one without fans, and while there is a suggested pn, however, no notes on thermostatic control. Should there be any, or just single speed? Haven't tried it out yet, but it sure isn't made in the fashion of earlier amps from what I can see.

[bfish]

Sorry, just honing my SA technique, I'm gonna need it the next couple of days.....

It's sorta like the difference 'tween a '69 and '79 Camaro.....they are completely different because of the 10-yr technology 'advances', but are both very good amps respective to their era. The '40 is not only heavier, but bigger in all aspects, especially the massive power supply. "Under the hood" is full....hardly room to fit in a golf ball anywhere....the unique PT has split primaries, allowing a handy "half-power" feature, activated by protection, or manually. True to Altec style at the time, they continually refined the amp, (factory mods), there are at least 12 revisions of driver boards, and 11 control boards. (NOTE-Someone should document the final revision details for posterity!). On the flip side, they're prone to bd-to-bd wiring issues, being done in that horrible period between soldered point-to-point, and dependable ribbon cables. IMO, there's a design issue with the control board being mounted on the heavy front panel, scads of control boards are broken when opened for service. Some parts are getting hard to come by. Still one of my most favorite.....

The '44A is also a product of its' time, the (single) fan is internal, but it still looks real empty in there.....very very dependable, clean amp if treated with common sense.

The 9440A has both bal. and unbal. ins, matching or bridging (internal) available, link out to parallel amps.

The 9444A has only Bal in, external matching or bridging.

[bfish]

There is no thermo fan control for the 9440A, full on to the back panel outlets with the power switch. There are 3 thermal-protection devices on the heat sink, a moxie for each channel half-power at 170 deg., and a main thermo-switch. If you can keep your hand on the heat sink under normal use, you're OK without a fan, but you need one otherwise. Lacking a fan shroud, you can easily fab one from sheet metal, and the fans are all over. If you're considering a variable demand setup, I find the changing speeds of the fan far more annoying than the continuous noise.

[bfish]

Charles,

I'd forgotten how far we'd already gotten on your project, and that we had a schematic (DUUHHHH!). Wet noodle time for me.....

Since the 9446 has an NTC thermistor paralelled with each bias pot for thermal compensation, I'd still suspect the thermistors as a likely source of problems (they're likely mounted on the heat sink, not the board).

The heat specs in the lit. show the 9446 to be cool at idle, but even at low driven levels to produce almost as much heat as fully-driven. If you're comparing two units, perhaps the other one is actually running too cold, as they do have extensive protection ITR.

I'm headed to Beggs, OK, for a few days of wood-cuttin' and lie-swappin' with an old friend, but will be available after, if I can be of help.

Brad

[cclark65]

I actually am comparing the channels in one unit. One heat sink stays cool, the other will heat up too hot to touch within 10 minutes...with no signal attached. I have to put a scope on it and see if there is some wierd HF stuff going on causing it, but haven't got that far. It's a spare amp, so it's no major issue, I have 2 others I can use for the drum monitor.