And to add insult to injury, while I was struggling to fix the power supply, a 54717A was sold on EBay :( I cannot hope the buyer is a member here...

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A friend is looking for a low voltage transformer and I have two of these from not economical to repair units that were parted out.

Looks to be hefty.

73
Glenn
WB4UIV

Why do you want to know? Are you trying to find a replacement or planning to use one in a ifferent application?

Roert G8RPI.

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-----------------------------------------------------------------------
Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv@...    AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license" 

Why do you want to know? Are you trying to find a replacement or planning to use one in a ifferent application?

Roert G8RPI.

Thanks Mark.? Yes, I realize that, I have two 500W resistors mounted on a large heatsink.
I will be testing NAD 2200 and 2600 amplifiers

--Victor

Hi Group,

I've done quite a bit of searching and so far I haven't been able to find how to exactly connect a power amp to an 8903B to make some basic measurements.
I know that the 8903B's signal generator can be connected to the audio amps input but what I have not seen explained is how to connect the amp's output to the 8903B
input. Am I correct in assuming the right way to do it is to have an 8 ohm or 4 ohm load on the output of the amp and connect the 8903B input in parallel with the load (at 600 ohms impedance)?

Thanks so much,
Victor

Glenn,

I have seen many various methods to empirically determine secondary current ratings of unknown transformers but a lot of them apply to either single secondaries or the larger utility distribution transformers.? If you have a working transformer with known secondary voltage(s) I have usually used a simple and sometimes less-than accurate method of applying a load to the secondary until the voltage drops 10-15% then measuring the current.

Usually the transformer manufacturers will specify the rated output voltage near the full load condition and the output is obviously much higher in an unloaded state.? But for smaller transformers one must also take into consideration of possible core saturation when nearing a full-load condition.? That can be observed with an oscilloscope while applying loads to the secondary.

Other numerous approaches taken have been taken and I am sure others will weight in on them but some either are not indicative of a true current rating for those transformers? with multiple secondaries or may be destructive when attempting to test. This is especially true if the transformer contains buried thermal fuses in the windings that may open upon an overload condition.

Contacting tech services of one of the major transformer manufacturers may also shed more light on how to determine currents.? As a sidebar I once did a design on a power supply and contracted with a small local manufacturer to produce the required transformer for the application.? The company actually was in the business of producing inclinometers for off-road vehicles but the engineer who worked there loved transformers so the company let him set up a small manufacturing facility to produce them.? The guy was a wealth of knowledge on transformer design and became quite a source of education on the subject. After all of these decades I don't see the company around anymore so off-road enthusiasts apparently trust the capabilities of their vehicles until they tip over.

Greg

Hi Jeremy,
sorry for the delayed answer! I did get your e-mail, but it looks like my reply did not make it through. I said yes to your proposal, just waiting for the final shipping cost. and your PP address.
Kind regards
Chris

Thanks, I'll contact these companies, but I'm not setting my hopes too high; they are all distributors that eye the corporate big bucks and don't care about the small fish in the pond. $170 for a month plus back and forth shipping plus Canadian taxes is about what a 54720D frame is worth, but I'd take it if available.

Hi Ovidiu:
I've got a 54720A frame.?
Best regards and wishes.
Roy

Does anyone have the ratings for HP 9100-4068 transformer?
This is from a 8566 spectrum analyzer.
The manual has voltages, but, no current ratings for the windings.

Any help appreciated.
Google was no help.

Glenn

--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

Ok, so I fixed the power supply (one dead mosfet) and now my dear 54720D is like a Schroedinger cat, dead and alive at the same time. It works, I configured everything that can be done manually (serial number, model, date/time, etc...) but without recalibration it only makes a nice door stop.

Really, anybody has a 54717A calibrator I could borrow for a ten minutes calibration job? I’m willing to pay back and forth shipping plus a realistic compensation for the trouble.

If not, this amazing scope is ready to go for target practice, fortunately with pellets only, here in Canada. I’d like to do the same with those designing this amazing scope around a $5 battery, without the possibility of self calibration.