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Electronics => Repair => Topic started by: LoTech on February 10, 2017, 02:32:19 am

Title: Panasonic VP-7723A
Post by: LoTech on February 10, 2017, 02:32:19 am
Hello friends,

I am new to EEV but I have to confess that I am a long time lurker. I am a huge fun of Dave and of this forum.
Electronics is an old hobby of mine and from once in a while I acquire a test bench instrument hoping that one day I will have more time to use them.

I now have an audio generator, analyzer, a Panasonic VP-7723, that appears to have a problem. The oscillator works fine, I can adjust frequency and amplitude and the display shows the levels for each, just fine. However, the problem is that the display turns off almost immediately after I stop turning the attenuation (knob). When operating the attenuation, the display comes back on, then it goes away once I stop.

I looked at the user manual, and if this is the intended behavior of the unit or there is a way to make it stay either on or off, but I sure missed reading that part..
I am inclined to believe that there is a faulty component in the unit that causes this to happen and wanted to know if anyone here is familiar with this audio analyzer or has any other suggestions.
Your help would be greatly appreciated!

Title: Re: Panasonic VP-7723A
Post by: Armadillo on February 10, 2017, 03:30:25 am
Panasonic VP-7723A is a audio analyser.
If after 2 sec from your adjustment, the display blank, then suspect the control assembly.
Because it suppose to alternate to the current measurement values.
Title: Re: Panasonic VP-7723A
Post by: LoTech on February 10, 2017, 03:51:59 pm
my bad..had the head in the cloud when I typed that...yes, an audio analyzer indeed.

Thank you for the pointer. I will look at the control assembly section.
Has anyone else experienced a similar problem with this unit? or one of its close siblings?
Title: Re: Panasonic VP-7723A
Post by: LoTech on February 10, 2017, 10:01:28 pm
Does anyone know of a source for the schematic for this unit?
Title: Re: Panasonic VP-7723A
Post by: LoTech on February 11, 2017, 04:46:58 pm
so after toying with this unit a bit more, I suspect a bit of newb, operator error could be the problem

When using the oscillator as a stand-alone oscillator, to feed the signal out, but with no feed-back loop to the input side of the analyzer, the oscillator display will turn off after I stop turning the attenuator, whether adjusting frequency or amplitude. The signal continues to be put out, just the display turns off. This is what I found concerning and I was asking for help with. I am still unsure that it is the expected behavior for this analyzer.

That said, when using a feedback loop to the input of the measuring section of the analyzer, the display of the oscillator, becomes a readout for the feed in, hence a frequency counter, looking at the output frequency + distortion (which is as low low  ;D). The oscillator is still active and can be adjusted. The frequency out shows up for the time the attenuator is operated, then it goes off and it is replaced with the the frequency in. The displays now stays on at all times.
I know my description is sketchy , but I know the unit is supposed to work this way when the feed-back loop is made, hence when the unit is used as an analyzer. I am now thinking that the unit is not intended to be used as a stand-alone oscillator and a feed-back loop is allays expected.

Could anyone that has experience with this unit confirm this? This does not appear to be a very popular unit, or is it?