Autotek model 7050 BTS (Like a 22)

[Dr Zeus]

Ive had this amp in my collection collecting dust. I know its like a Punch 45HD or possibly better in the same class (but not as good as say an Orion HCCA 225). I think the only difference between this and an Autotek 22 is that this one has a riser board with thru-hole components, where the 22 used Zed Audio proprietary components.

This amp works, or was working, until it fell off the shelf and snapped the pot for Treble control. I can handle this repair no problem of course.

Question; while taking the amp apart, I noticed IRFZ40 being used in the PS, and one has a LOT of water/corrosion like the rest of the amp (surface rust). I'd like to maybe replace the two since I've got this amp now apart, but IRFZ40? Can I use IRF3205 for some added competition? This amp will likely never run in anyones car regardless of PS fet, unless I dream up something cool and personal in a <45w class.







Thanks!

[Perry Babin]

I think these amps may use only a 100 ohm resistor (no PNP driver transistors) to pull the gates down. If so, if you use 3205s, change the gate resistors and after getting it back in the sink, reduce the 12v power supply to about 10v. If the current draw increases at lower voltage, it means that the FETs aren't being driven off efficiently and you'll either have to use a different FET or make modifications to the circuit.

[Dr Zeus]

The gate resistors appear to be 100ohm, but are measuring 93 ohms each. You did say change them, but to what? I have a few different values available under 100 ohm; 22, 47, 68...

You are right that the TL594CN is driving these directly through a resistor. No drive circuitry assisting.

[Perry Babin]

47 would generally be what I would use but here, you may want to use a lower value because the pulldown is weak. You'll have to experiment and test if you want to modify the amp.

[camusmuse]

.....a little off topic, but I dont think its really fair to compare the 7050(unless its an XX series) to an Orion 225 HCCA. The Orion HCCA is a high current unregulated amp if I am not mistaken. Its "low" current version is the 275(75watts x 2). So an Autotek 7150(also 75x2) might be closer, but it still is a regulated amp.

I have owned and used several of each. The 'teks have been alot more reliable, and they know when to shut down; where as a 225 will put out a ton of power you have to actively cool it, and still have to make sure doesnt blow.

Also, IMO...the 'teks have a cleaner sound, but of course that is subjective.

I am certainly not an expert like mr Babin, so I ask this.... Is the Orion a better designed amp or is that just OP's opinion?

Thanks for the info.....