Astron discussion

Jeff has been working on the Astron supplies for a couple years or so and have found some issues with them.

Here's Jeff's call to the vender:

For those interested in the Astron saga, I finally managed to talk on the phone to a couple of folks at Astron, here is their response to my questions:

OK, first I talked to a sales person then he passed me on to a rather heavily accented technician, not that it means anything, other than obviously the technician could not have had a lot of history with ASTRON!

D5 in backwards – lack of QC! I always give the amateurs that I work on their PSU's the option of buying a new board, and therefore the most recent changes, or have me modifying their old board. Naturally I suggest a new board for the oldest versions of your PSU, because to add the various components makes the board look ugly, and of course is more work for me, given I do not charge for my work, I lead them towards the most expeditious route, and finally it helps your bottom line!

He stated this was just an error in manufacturing! To which I stated that the implication is that they have no quality control! He then added they are in the process of changing subcontractors. Gee, I hope the new subcontractor has some QC!

Why after 50 years of manufacturing is C10 (0.01 MFD) missing from all recent boards purchased!

I was told it was not needed ! (WT Heck after 50 years?) This is between the base and collector of the driver transistor, and was there to prevent any oscillations in that part of the circuitry. 

Why after 50 years has a new 0.1 MFD Capacitor been added located physically on the back of the board, from Q2 base to junction of R2 and C2 (also 0.1, and now in series with C2 effectively reducing the capacitance of C2.)

He was not clear on this, merely that they had added another capacitor and didn't get around to explaining why or why its present location and path.

Why after 50 years has C11 changed by a factor of 100,000 from a 0.001 MFD (RF killing capacitor) to a 100 MFD electrolytic with negative on CL pin 2 and positive on CS pin 3, (sense of output) effectively dampening the change rate of CS (Sense)

Done to radically slow down the sense as I suspected, and had to do with complaints of people turning on power supplies with the load already near max, and the power supply shutting down on power up.

Why after 50 years has another 22 MFD capacitor across connection 1 (SCR Gate) to connection 3 (GND) been added, effectively in parallel with C6 (22 MFD) and C102 (0.1 MFD). If needed, why not just one larger capacitor?

Done as I suspected to slow down the SCR gate actuation in high RF locations. When asked why they put a second 22MFD instead of a 47 MFD or similar, he said they don't have those parts, so it was just a matter of inventory.

Is the 2013 schematic the latest version? If so it does not show any of the above changes.

Apparently, (since they did send me a 2020 version of an RS-35A/M schematic) even the newest schematic does not show all of these changes (C10 is still on the schematic, several components are unmarked and the eletrolytics are not marked as such).! I pointed out that what they are doing is shipping products with a schematic that does not reflect the product. He stated that some manufacturers do not even give customers schematics. To which I said yes, SAMLEX a Chinese company, but ASTRON is a well respected AMERICAN company, who has had a history of providing schematics.

He offered to let me talk to his boss, but he was not in the office at that time, but would communicate with further as they have my email address.

There are other errors on 2013 (and also on the 2020) schematic (connections to TIP 29 collector, and C10, and to Q100, are not drawn as all other connections, with a spot at the connection. Also from Emitter and R4, and the Triangle indicating select on test components, missing from R7X and R3X)

He said it takes time to draw schematics, he could give me a hand drawn one, but to do it on a computer takes time. I told him he needs to tell someone that they need to take the time, because what they are doing is providing a schematic of a PSU which is not that which they are providing their customers.

What purpose does R2 serve? It only connects to the capacitor C2 (0.01)

I did not get to this point 

The change back and forth from discrete rectifier diodes to bridge rectifiers and back again, was this just a change made because of availability of parts or is there some compelling reason for these changes. On 35A and lower current models (the majority of what I have worked on, I simply use a 50A bridge rectifier, or multiple thereof on larger PSU’s. When the discrete diodes were located on the bottom of the chassis, they would occasionally get shorted by someone allowing something metal to roll underneath the supply. Likewise when they were located on the heatsink at the back, people would stack their radio on top of the supply, and drop a coax connector when disconnecting the radio, thereby shorting the diodes and or the pass transistors.

I also did not get to this point.