Tek AM503 Amplifier Design

[TheContractor]

Hello all, I recently purchased a Tek current probe/amplifier pair and after checking it out immediately started to think about how modern technology could improve this ancient amplifier. Before I start simulating and working my way through the circuit, has anyone attempted this? Google brings up very little on the topic of modernizing the AM503 short of just buying a newer Tek amplifier but it seems like it shouldn't be too difficult. The main hurdle I see is the process Tek used to build these included hand matching parts together and I don't fully understand the implications if that isn't respected.

My first goal is to recreate the circuit board as-is with SMT parts. Once that's proven then I'd like to look at miniaturizing the the amplifier/power supply set.

[georges80]

I use an AM503B which is a much nicer amplifier than the older 503 (with the mechanical switching mechanism inside).

Are you looking to upgrade the B or the older model?

cheers,
george.

[TheContractor]

I have the original AM503 (not the AM503B). I assumed the 'B' probably had all the same drift issues and other quirks the old one did, but what has your experience been?

[georges80]

The 503B is a different beast than the old 503 boat anchor.

I'd suggest buying one. I had a 503 and got rid of it when the opportunity came to pick up a good condition 503B.

The drift is minimal after warm up and a few degauss cycles. The 503B tells you when it feels a degauss is needed and you just unclamp, close the clamp, press the button, listen to a bunch of clicks and clacks and you are good to go.

I've had the 503B on for many hours and have not seen drift issues. Of course with any magnetic probe/clamp, if you are after accuracy you need to realise that external magnetic fields (even the orientation versus planet earth) need to be addressed in your degauss/probe position.

Anyhow, I'm very happy with the 503B and have been using it for 5+ years without problems with an A6302 probe.

cheers,
george.

[TheContractor]

Thanks George, I appreciate the info on the 503B. Looks like I'll be trying to offload my two 503s.

[icpart]

Hello all, I recently purchased a Tek current probe/amplifier pair and after checking it out immediately started to think about how modern technology could improve this ancient amplifier. Before I start simulating and working my way through the circuit, has anyone attempted this? Google brings up very little on the topic of modernizing the AM503 short of just buying a newer Tek amplifier but it seems like it shouldn't be too difficult. The main hurdle I see is the process Tek used to build these included hand matching parts together and I don't fully understand the implications if that isn't respected.

My first goal is to recreate the circuit board as-is with SMT parts. Once that's proven then I'd like to look at miniaturizing the the amplifier/power supply set.

I have same interests as you for modernization of AM503 amplifier. You can find modern variants like AM503B but in most cases they are to expensive even for old used item. AM503 is far cheaper from AM503. Very interesting is that I can't find any Service manual for AM503B but in Internet you can find SM for AM503A which is also Digital controlled amplifier like AM503B and also i think it is previous model before AM503B. AM503B is just upgraded variant of AM503A i think.