Amber 3501A Distortion analyzer?

I have one and really like it. Built in Montreal in the eighties by Amber Electro-design. Wayne Jones and Ed Meitner did the design. I was able to buy a manual reprint from Wayne a few years back.

They came with a variety of options, do you know what it has? If not, I could translate the model number for you. It is on the rear.
 
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I have one and really like it. Built in Montreal in the eighties by Amber Electro-design. Wayne Jones and Ed Meitner did the design. I was able to buy a manual reprint from Wayne a few years back.

They came with a variety of options, do you know what it has? If not, I could translate the model number for you. It is on the rear.


I found the 3501 manual (not ''A'') online.Quite impressive!

According to the seller,the S/N is 3501-0100,which seems to be one short.
According to the manual,the second serial # set should have 5 numbers,so perhaps he's misread the number.He says it doesn't have the battery option,and made no mention of a frequency counter. That leaves the intermod or ANSI Filter as possible options.Sure hoping for intermod:rolleyes:
 
Well,I ended up getting an Amber 3501(not A).Model # 3501-23019. Actually,I ended up with three of them!
They all have the same 3 options: internal heavy-duty battery pack,balanced output and frequency counter.One has a factory ''custom'' filter option,but I can't find any information on the type.
Although the cabinets are a little rough (worn & scratched paint,but no dents) the face-plates and meters are perfect.All knobs and switches are present and functional.These models have the external power packs,and the wiring is somewhat tatty.
I also got the complete operator/service manuals,although they are for the later,internal transformer model.
 

audio king

Member
2014-09-06 3:28 am
Thanks Demian!

The build quality of these is very impressive,and as you mentioned,the batteries are toast.Not needed though,as I'll be using them on my bench.

Two of the unit's meet or better their osc distortion specs,although the third is slightly above the published level.Some of the rotary switches are a bit erratic,probably from not being used,which is upsetting the stability of my readings.

The manuals I received with them are the same as what's available for download on the net.

My machines are loaded up with phone filters,and the front panels are actually factory-labelled for these: 3khz flat,15 khz flat,pgm wght,ccir 2 khz.

One unit has the ''C''-type filter on the 5x5 circuit board,for which there are 6 possibilities,and there is no indication which one it is.

I would really like to find more information on the active filters (B&C types),as the only information in the manuals is for the passive (A) types.

Finding the IMD-option board would be nice too,but that's not likely!

Cheers,

Art


For some reason,I can't upload the photos; system says ''security token missing''
 
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So I picked one of these Amber 3501's up a couple of months back and I thought I'd resurrect this thread. The one I bought is a stripped down 3501 with the 358 hi-res freq meter option being the sole add-on. It came with the phone filters, 15k flat, 3k flat, psopho and also "A" weighted. According to the serial number it appears this unit was manufactured in 1988. I got lucky and the one I bought has a faceplate in near mint condition and seems to be working quite well.

I went through and reconfigured the filters for the normal audio range of, 400Hz HP, 30KHz & 80KHz LP and I left the "A" weighted alone.

I've had some time to use this meter and I'm surprised it doesn't have a bigger following with the DIY crowd. The footprint is decently small, it has user configurable filters and it has both -90dB and -100dB ranges (something I wish the 339A had) and it comes standard with both single ended and balanced inputs. The price is also decent (I paid < $200 shipped) and there appears to be reasonable availability on the used market.

The unit I've got here is measuring .0007% with the 30kHz LP filter active and rises to about .0009% with the 80kHz LP. The 3501 also has socketed chips throughout so it seems like its just begging to be tweaked to improve the performance. Has anyone out there tried any parts changes on these to improve the performance? It looks like 5534A's are used throughout much of the oscillator and input circuitry.

I'll probably go through it and perform a recap to begin with. There are a ton of 10uF electro's in a variety of locations.

In case anyone would like to see the schematics, here is the operating and service manual on the web.
 

audio king

Member
2014-09-06 3:28 am
After doing some minor repair and restoration work on my own machines,I was amazed at how well these perform.With careful calibration,these will easily hold their own against any modern machine,and can outperform many.

And that small footprint certainly preserves bench space.My Rohde & Schwarz is an absolute monster by comparison.

Welcome to the Amber club:)
 
I've owned an ex Royal Canadian Navy 3501A for nearly 20 years now, a recap now is definitely a good investment.

Great little instrument that has long since earned a permanent space on my bench.

I've had a transformer go west, a tantalum fire**, and a reed relay failure in the years since I first got it. I purchased a parts unit for transformer and relay, and I am happy to report that over the past 9 - 10yrs other than doing a recap I have not had a lick of trouble with it.

** The tantalum fire was quite exciting as with the covers on I could not see what was going on, but there was an "odd burning smell" coming out of it. I removed the top cover in less than 30 seconds and there was a candle, err burning tantalum supply bypass cap which I quickly extinguished. Fortunately there was no other damage.

FWIW A tantalum cap probably IS required in any location you find them, I replaced them all with low impedance EL caps and I now just barely meet the distortion specifications, whereas before the fire I met them with lots of margin. It's still rather good as you might surmise.

I would resist the temptation to "improve" the design with more modern op-amps, there is the potential for a small improvement or for unrecognized mischief to occur. There are a few op-amps that offer slightly better noise and distortion performance than the 5534A but probably not meaningfully so in this context. It was designed to operate reliably with the characteristics of the 5534A that Amber was sourcing in that day, for that reason I wouldn't replace any that are not demonstrably bad.
 
If I recall,all of the tantalum caps are used for nothing more than PS bypassing,but in the more critical areas.

When I considered how many electro's were used for decoupling in this unit (you need an entire bag of 10/40's!) I realized that the tantalums were expressly spec'd for specific sections.

I didn't wish to continue with tantalums,so instead went with plastic films. These are available from several suppliers in the needed 1, 1.5 and 10mfd values,usually in the 63v variety.
 
Its great to hear of you guys experiences with this analyzer.

I had noticed that some opamps were bypassed with EL's and others with Tantalum's. So I had surmised that the designers had used the tant's there for a reason. My plans were to replace the tantalums with tantalums. I typically go up one voltage range on a tantalum when I replace it. I do not know if that is really buying me that much but it's typically not that much more expensive to move from a 25V cap to a 35V one. On the EL caps, I have a nearly full bag of 22/50 Panasonic FC's in one of my parts bins somewhere that'll probably get used in place of the 10/40's.

I definitely do not want to do anything to compromise the performance of the stock unit. I primarily mentioned the op-amp changes because I know that many users here on DIY-A have greatly improved the performance of the HP 339A, Shibasoku, Boonton, and other analyzers. I was hoping maybe someone had experimented on the 3501 before.

I went through the calibration on mine yesterday and at certain sweet spots in the freq band I'm getting -105dB with the 400 HP & 30kHz LP filters active. A side benefit of recaling is the meter deflection and drift on the low end of the range is only about .25dB now. Before the calibration I was getting up to 1dB of meter drift in the -100dB range.
 
Cal or no Cal.?

Its great to hear of you guys experiences with this analyzer.

I had noticed that some opamps were bypassed with EL's and others with Tantalum's. So I had surmised that the designers had used the tant's there for a reason. My plans were to replace the tantalums with tantalums. I typically go up one voltage range on a tantalum when I replace it. I do not know if that is really buying me that much but it's typically not that much more expensive to move from a 25V cap to a 35V one. On the EL caps, I have a nearly full bag of 22/50 Panasonic FC's in one of my parts bins somewhere that'll probably get used in place of the 10/40's.

I definitely do not want to do anything to compromise the performance of the stock unit. I primarily mentioned the op-amp changes because I know that many users here on DIY-A have greatly improved the performance of the HP 339A, Shibasoku, Boonton, and other analyzers. I was hoping maybe someone had experimented on the 3501 before.

I went through the calibration on mine yesterday and at certain sweet spots in the freq band I'm getting -105dB with the 400 HP & 30kHz LP filters active. A side benefit of recaling is the meter deflection and drift on the low end of the range is only about .25dB now. Before the calibration I was getting up to 1dB of meter drift in the -100dB range.

Hi KC,

I have several units which might be called "rough" condition, seems the more used units presently work the best? I just made up a laptop power supply for the 3501, which only has pins 2&3 for the external input of a power supply, that is for an AC transformer, but the DC switcher from an old HP laptop at 18.5 volts and up to 4.94 amps is fine going through the bridge and Main regulator, as I think this Amber 3501 set really only draws about 12 to 15 Watts, maybe an even smaller wall wart supply would do the job, I may try one at somepoint.

I suspect the careful use of AD797's in 3 or 4 places might improve the set overall, but my later sets (the 3501A's) are doing not so well, into the 70dB and the 80dB ranges, while the 3501 is giving me 92dB without filters, and 97dB on loopback for 80Khz. bandwidth. This is for no adjust or cal, or null or anything. Like I said these sets are rough, and three had smoking tantalum's, while two had blown primary fuses, and burned tantalums.

-Steven

I also think that the older unit with the switcher supply, and the additional shielding, which also has lots of room inside could be adapted to the newer lithium batts, as the charger is quite sophisticated and maybe 12 Amps from six 18650 lithium batts could run the set for over 12 hours, with almost no increase in weight. There are boards to charge multiple 18650 cells made, just add batts!
 
Hi KC,

I have several units which might be called "rough" condition, seems the more used units presently work the best? I just made up a laptop power supply for the 3501, which only has pins 2&3 for the external input of a power supply, that is for an AC transformer, but the DC switcher from an old HP laptop at 18.5 volts and up to 4.94 amps is fine going through the bridge and Main regulator, as I think this Amber 3501 set really only draws about 12 to 15 Watts, maybe an even smaller wall wart supply would do the job, I may try one at somepoint.

I suspect the careful use of AD797's in 3 or 4 places might improve the set overall, but my later sets (the 3501A's) are doing not so well, into the 70dB and the 80dB ranges, while the 3501 is giving me 92dB without filters, and 97dB on loopback for 80Khz. bandwidth. This is for no adjust or cal, or null or anything. Like I said these sets are rough, and three had smoking tantalum's, while two had blown primary fuses, and burned tantalums.

-Steven

I also think that the older unit with the switcher supply, and the additional shielding, which also has lots of room inside could be adapted to the newer lithium batts, as the charger is quite sophisticated and maybe 12 Amps from six 18650 lithium batts could run the set for over 12 hours, with almost no increase in weight. There are boards to charge multiple 18650 cells made, just add batts!


I don't know how but I missed this post from a few months back.

I agree with you that a few properly placed 797's would help the 3501's performance. If they weren't $11 each I'd probably have a handful. I'm using the LME49710's which are < 20% the cost. The 49710 will be extinct in the DIP8 package soon though so buy some if you want them, both Digikey and Mouser have them flagged for EOL. I doubt they'll be restocked once the existing stock is exhausted.

I spent a good bit of time and went back through my 3501 & 3501A recently. I have the 3501 at -103.5dB @ 1kHz now in loopback with the 400HP and 30k LP active. I have the 3501A down to -105.5dB @ 1 kHz with the same filters active. The 3501 has a high 3rd harmonic that is coming from the oscillator and I've yet to track the source of it down. If I connect my tweaked 239A oscillator up to the 3501 it measures right at -106dB with the same filters active.

For now I settled on 49710's at U1008, U1030 & U2008. I had 49710's at several locations in the oscillator of both units but the 3rd harmonic came up by about +12dB with them installed so I put the 5534A's back in.

I still need to pull the freq tuning pots out of my "A" and clean them up. This unit is noticeably noisier when its mid-band and still on the pots, if I tune it fully to above "10" to where all four tuning pots are at the end of their travel I get substantially better noise performance. I've found that this is a pretty good sign that the pots in one of these units are dirty and need to be cleaned. That's a fun process, the individual pots do come apart rather easily once desoldered from the board and you can easily get some deoxit into them at that point.

IMO these units really are the best bang for the buck in analog analyzer's as long as you don't mind doing the standard fixes. This is especially true now that the HP 339A's have exploded in price. After having a modded 339A for a period of time I much prefer the 3501 to the HP.
 
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I don't know how but I missed this post from a few months back.

I agree with you that a few properly placed 797's would help the 3501's performance. If they weren't $11 each I'd probably have a handful. I'm using the LME49710's which are < 20% the cost. The 49710 will be extinct in the DIP8 package soon though so buy some if you want them, both Digikey and Mouser have them flagged for EOL. I doubt they'll be restocked once the existing stock is exhausted.

I spent a good bit of time and went back through my 3501 & 3501A recently. I have the 3501 at -103.5dB @ 1kHz now in loopback with the 400HP and 30k LP active. I have the 3501A down to -105.5dB @ 1 kHz with the same filters active. The 3501 has a high 3rd harmonic that is coming from the oscillator and I've yet to track the source of it down. If I connect my tweaked 239A oscillator up to the 3501 it measures right at -106dB with the same filters active.

For now I settled on 49710's at U1008, U1030 & U2008. I had 49710's at several locations in the oscillator of both units but the 3rd harmonic came up by about +12dB with them installed so I put the 5534A's back in.

I much prefer the 3501 to the HP.

Hi KC,

I have plenty of Amber 3501A sets to play with, I hope I can get results similar to yours. Yes, the price on the AD747 parts seem to be just all over the place, mostly too high. Then, they have "A" parts, AN, ANZ, BN, BRN, and ceramic SQ's, some have ANalog Device logos, some don't - what a mess???

I bought some older stock AD747AN's DIP's, and also some LT1468CN8 DIPs, at less than half the price, these are low noise, 90 Mhz. parts and in almost all ways are very nearly identical to the AD747AN's at 110 Mhz. However, the LT1468CN8's are tuned for lowest noise using pin 8 at the factory, so you have to remove pin 8 to avoid problems :eek: in "other" circuits that may try to use pin 8 for compensation.

I will try both the AD747 and LT1468 parts in the three positions you used, and see what results I get. I might also try the LT1468's, or another TI part, in the Oscillator and see what happens, I think I have a few of those 49710, 49720, or 49722's somewhere, if I can find them. I also plan to use 22 uF / 35 volt tantalums in place of the "10" uF parts because these IC's draw more current than the original NE5534AN's did, maybe as much as twice as much current. What fun!!!

I will eventually report back in a matter of weeks (I hope).

Steven
 
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I look forward to hearing about any improvements that may be found. With my stock 3501 at 1V at 1KHz, with the filters on, I get down to .00115%. Like Kevin, I’m mainly a tube guy, so it’s more than adequate.

First order of business for me is to convert the auxiliary filter from C Message over to something more useful to me, A weighting.
 
You should be well below -100dB @ 1kHz with the 30k LP filter active. Bring the output level up to as close to max at the 0dB setting as you can get, it'll probably be around 1.2V out, you'll get lowest distortion from the oscillator with max output. Also make sure your on the 10 X 100 setting and not 1 X 1k because distortion will be lower on 10 X 100. As I pointed out in my earlier post in this thread also bring your freq selector dial up a little ways past 10, you will reach a point where all 4 tuning pots hit their limits and the distortion will be even lower. Those settings are how I've been evaluating my Amber's.

With mine set up like this I will see approximately -105dB with the 3501 cold rising to about -103dB after about an hour of sitting and warming up.

My 3501A doesn't suffer from the rise in noise from heating and it sits right at about -105dB.

In the end I'll probably end up selling one of my 3501's due to the fact I'm now using an AP system one that I bought a few months back so the 3501's will not see as much use.