Amber 3501A Distortion analyzer?

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Its been almost a year since there was any action here. however I decided to go through my collection of audio test stuff and start moving on the ones that are not useful to me. (9 is too many right now!!) So I'm going through and tuning up what I have before offering them for sale.

I have a 3501-21119. It has the balanced option (but no transformer?) and IM and 400Hz HP, 80 KHz LP and 20-20K bandpass and CCIR 2 KHz filters. It has the battery option (I removed the batteries which were dead but still have the case) and I got it without a power supply so I modified it with an external Jameco desk wart (too big for a wall wart). I'm sharing notes for anyone who needs some guidance in solving these problems.

The power supply is a Jameco 2082564 and i found a matching connector for the unit that fit in the existing hole.

With the balanced interface the meter cal process does not match the unit. Some of the cal process is probably wrong anyway. the trim pots are clustered around the meter accessible from the bottom. I could not work out a correlation and the board is not in the documentation I have. Setting the meter was a bit of try each pot and see which is which. The notes i took were: R1128 adjusts the -10 dB end and R1122 adjusts the 0dB end AND they interact. I think R1129 is meter sensitivity but by then if the meter was within a pointer width I let it pass.

Another gotcha- There arfe instructions for nulling HD2 on both source and analyzer. I had trouble with those. I could not get the HD2 down using one of Victors oscillators as a source. Rolling opamps or other efforts requires dismounting the IM board assembly. That requires dismounting the power supply bracket since they all interfere. With the battery out however the supply module is light and can be supported by its wires.

Also this unit has an oddball 1/4" connector set up for Western electric plugs with a small diameter tip and the normal plugs don't fit. I think a Neutrik connector would fit the PCB but have not tried.

This has the frequency counter on the lit and the assembly can be removed easily by disconnecting the three cables with no impact on operation.

In any case I'll be selling it. if anyone is interested before it lands on eBay drop me a note.
 
Hi Demian,

Funny how I had mine out to our local Toronto gathering this weekend to test out a few pre-amps others had brought in, asking me to test them out.
I am happy with mine, pretty much the same options as yours except a "C" weighting filter for telecom use.
Mine is mint and was hardly used. I have a spare one for parts, so thinking do I need another one, maybe if the price is right :)
If Dilbert is around he might want it.
IIRC the balanced plugs are bantams, I have used regular 1/4" mono iirc they worked okay.
Thanks for your notes. I agree the cal documentation is questionable.
 
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The 1/4" stereo works fine on the input jack but does not connect at all on the output (PC mount) jack. I have not seen the bantam name in many years which is why I did not remember it. The 3501 is a really nice small unit and can give exceptional performance. this one doesn't quite make it to .001% and it has a "match" where the H2 of the generator syncs perfectly with the H2 of the analyzer. However both are wrong. It would be fun to dig deeper but I have another Shibasoku coming and just don't need another project. . .
 
I date myself with the bantam term, at least I remembered it from my telecom days :)
I think I would be spend my time on the Shibasoku too.
I was talking to a friend at the meeting going on about his AP55x, seeing stuff that other gear can not, features galore and I am playing with my 3501 toy, pale by comparison. Oh well it does what I need for a hobby.
iirc mine is doing about -103dB @ 1Khz with 400/30KHz filters. Would be nice to get one of Victors oscillator and measure the analyzer performance.
 

PRR

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There's 1/4" telco plugs and a smaller size for dense jackfields. I think "bantam" is less than 1/4".

The true telco 1/4 has different tip profile than Switchcraft low-price 1/4", but they often inter-plug OK.
 

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This unit has a connector by ADC that is specific to the "longframe" in the picture. The last step in the molding is smaller as are the leaf setup. There is no way a normal connector would fit. I'm waiting for a connector to help retrofit a battery and when that arrives I'll open it all up and attempt replacing the connector if I have an alternative that will fit.
 
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The particular jack in this Amber was made by ADC and they don't seem to make them anymore. The last step is molded to the smaller size. I got some new jacks but they have a different footprint entirely and will not fit.

I got the new battery installed and its all charging nicely.

Unfortunately its got to go on the block to make room for other stuff.
 
I have got two 3501A. After repair and adjustment they both show near -102/103dB.
I'd be happy to impove their performance for couple of dB and ordered LME49710 and AD797 to have a try.
It was mentioned here that 49710's were used for replacement of U1008, U1030 & U2008.
I found U1030 (it's an output of Preamp on the page 1 of schematic) and U2008 (it's an output of the Notch Summing Amp on the page 9), but i haven't managed to find U1008 position anywhere.
It looks like my set of schematic has some differences or it was some typo with U1008 mentioned.
I'd be happy if someone give me a clue.
 
I'm extremely thankful for your replies, guys!
Special thanks to Chamberman and my best hope that you will find the piece of time to determine exact IC's position numbers which were replaced to obtain better performance.
I've already tried to replace some singular 5534's but couldn't get visible improvement. It will probably become significant when all necessary ones are replaced together.
 
I have a 3501, full of blue tant's, two have failed on me, one in the PS, inside the can, PITA that one, yes they all should be replaced, but I only use it once in a while so I take my chances every time I power it up. Also keep the ext transformer off AC until i use it.
 
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