A Oscilloscope Operating and Service Manual. Part Number: ( Aug 76). The A is no longer sold by Keysight; this manual is provided for. To buy, sell, rent or trade-in this product please click on the link below: http://www · MODEL A. OSCILLOSCOPE. HEWLETT-PACKARD COMPANY/ COLORADO SPRINGS DIVISION. GARDEN OF THE GODS ROAD, COLORADO.
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The Vertical trace is way south and the vertical adjustment pots have little or no effect. I have digital electronics experience, but no idea what voltages to expect on an oscilloscope. A old thread by Jim Yanik recommended shorting the vertical deflection plates to each other, which did result in a correct centered bp. All power supply voltages are OK. There was a burnt connector pin and dry joints on the screen illumination side which I repaired.
With the A probe on the Cal 1v, only channel A selected and the vertical position pot on MAX, I can see the square wave pulse at the botton of the screen.
Volt on 1st deflection plate When vertical 17740a pot to MIN the Adjusting lowering the vertical posion pot up lowers the top part of the square pulse signal trace, the botton trace of the signal is fixed ho at the botton of the screen, and does not move. I do not know what the correct deflection plate voltages should be, or what the difference in the 2 voltage should be for the signal trace to be correct or visible on the screen.
I have measured Base reference voltages on both transistors is correct at 12v. I do not know what is lowering this I am now stuck and at the end of my voltage!!. Can anyone help or advise? Post a scanned image of the Scopes Yamp’s circuitry [ from the manual]the bp that covers the Y inputs to the Y plates will be enough for starters.
Hi Eric Thanks for the reply. I am in the process of scanning the diagram for posting Regards Barry. Hi Eric I have attached the pdf. HP A – A5 vertical output 1740 I would suggest the most likely cause is the large hybrid output device, labelled A5A1?
Barry Fox New Member Jul h, Voltage on Q5 collector 34v circuit shows This voltage does not change when disconnecting the 2 wires mentioned above. Thanks for your follow up. Hi Eric All the actual voltages are in Red as indicated in the circuit, with wires connected. Adding the Hhp resistors should give you a central Y trace display. Hi Eric Thanks for the info. I had some stripping to do, to reach these circuits, to be able to take the readings.
I will now proceed with your other modification and advise you of the results tomorrow. Barry Fox New Member Jul 9, Hi Eric Have done the modification with the results attached. I had to cut the tracks, as the chip is a flat ceramic type, with spring clips on th PCB. HP A Vertical Mod Adding the two R has shown that the two left side transistors are correctly biassed.
The two transistors inside the right side block are not biassed correctly. Hi Eric Attached are the requested voltages. I will have to start searching for the Chip ASA1, or a complete vertical deflection card. Do these voltages comfirm you suspicions?
HP A Vertiocal Amp additiona voltages Attached are the requested voltages. Barry Fox New Member Jul 11, Good morning Eric Thank you so much for all your assistance. I will search for the IC and let you know the result, if I find one.
Antique Radio Forums • View topic – Just got an HP A
Mikebits Well-Known Member Jul 11, Eric, you da man. Thank you so much for all your assistance. Barry Fox New Member Jul 12, Hi Eric Not much luck in my search for the spares.
I do have an attachment to this scope. Unfortunately, I do not have the knowledge to 1740w the circuit or which current components to use. Not much luck in my search for the spares.
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