Re Manuals: go here:- http://www.big-list.com/usedmanu.html this is the best list I know of. Manuals Plus and Manual Merchant seem to be the best of them.
RE KH distortion analyzers. I have had several and still have a 6880. It needs some work, the autoranging locks up. It works pretty well otherwise and so did the 6901 I had but the residual was .002% at best. I could not tweak or modifiy it to get better. It has an auto bandlimit filter to restrict the measurement to the first 5 harmonics.
The 4400 Oscillator is much lower distortion than these. I will break down and get a manual for the 4400 soon.
Tek obsession- here is a guy (Stan Griffiths) who has more than any of us could posibly manage http://www.reprise.com/ash/clients2/stans_collection.asp
-Demian
RE KH distortion analyzers. I have had several and still have a 6880. It needs some work, the autoranging locks up. It works pretty well otherwise and so did the 6901 I had but the residual was .002% at best. I could not tweak or modifiy it to get better. It has an auto bandlimit filter to restrict the measurement to the first 5 harmonics.
The 4400 Oscillator is much lower distortion than these. I will break down and get a manual for the 4400 soon.
Tek obsession- here is a guy (Stan Griffiths) who has more than any of us could posibly manage http://www.reprise.com/ash/clients2/stans_collection.asp
-Demian
Tucker http://www.tucker.com used to sell manuals. I bought some; at the time the prices seemed sort of reasonable, (not TOO much more than I'd paid for the instruments) and the copies were decent quality.
That generator may be the same internally as several others on the market. Its from a period when Tek was trying to sell service level instruments to a market full of good Taiwan product. Protek or Leader or JDR may have the same generator with different graphics on the front. I may be wrong but you will find the circuitry to be similar if not the same.
What is the problem with the generator?
-Demian
What is the problem with the generator?
-Demian
50-something millivolts of offset, frequency is off (that doesn't bother me too much), like to see if I can get the HF square wave to look a little better. There is a wierd discontinuity in the pos and neg peaks of the sine wave that I'd like to see if I could get rid of. And THD is at about 0.25% or so, which meets spec, but I'd like to see if it could be improved on.
The offset is what really bugs me (has caused some minor problems and I've had to account for it)...I'm certain there's an adjustment, and I can see the output amp on the board, but there are 5 trimnpots in close proximity to that section and I'm loathe to just start twiddling them to see what happens. The entire unit must have upwards of 25 trimpots altogether.
There is nothing on any of the boards to indicate a manufacturer.
The offset is what really bugs me (has caused some minor problems and I've had to account for it)...I'm certain there's an adjustment, and I can see the output amp on the board, but there are 5 trimnpots in close proximity to that section and I'm loathe to just start twiddling them to see what happens. The entire unit must have upwards of 25 trimpots altogether.
There is nothing on any of the boards to indicate a manufacturer.
The service manual for the cfg is really HARD to get. If you are really in need, I guess a phone call, mail or even letter to a Tektronix Service center or main office will be the only chance. Try to get through to the service guys, mostly the elder are really willing to help.
The cfg is made under the high market pressure (a product that has to be sold cheap, so the design is accordingly). Don't compare it with older Tektronix gear - the cheap new stuff has the plastic handle to ease the "throw away when broken".
sorry to speak so openly, but even Tek had to follow the market. Others too: Wndel&goltermann, excellent LF Genrators and spec analysers, went down in reputation when bought by Wavetek.
So no complain on the newer test gear. But the maret has it's rules: If you buy cheap, it is cheap. And "cheap" not in the range you yourself call it cheap/expensive, but as a professional does.
so terribly sorry: Don't expect too much healing in your CFG with a service manual. Before the case turns hopeless: Buy a better genrator on the 2nd hand market.
The cfg is made under the high market pressure (a product that has to be sold cheap, so the design is accordingly). Don't compare it with older Tektronix gear - the cheap new stuff has the plastic handle to ease the "throw away when broken".
sorry to speak so openly, but even Tek had to follow the market. Others too: Wndel&goltermann, excellent LF Genrators and spec analysers, went down in reputation when bought by Wavetek.
So no complain on the newer test gear. But the maret has it's rules: If you buy cheap, it is cheap. And "cheap" not in the range you yourself call it cheap/expensive, but as a professional does.
so terribly sorry: Don't expect too much healing in your CFG with a service manual. Before the case turns hopeless: Buy a better genrator on the 2nd hand market.
Nothing you have said suprises me...the 253 was built cheap and designed to be sold by the hundreds to tech schools and such.
So I'm not exactly unfamiliar with its intended market niche. But, when working as intended, it does what I need it to do as long as I'm not needing a super-clean signal. But a small misadjustment here and there is no reason to throw it in the trash. With a manual I could very likely cure the issues in an hour.
Trying to get a Tek service technician on the phone is like trying to dial up Presedent Bush. Pretty slim chance.
So I'm not exactly unfamiliar with its intended market niche. But, when working as intended, it does what I need it to do as long as I'm not needing a super-clean signal. But a small misadjustment here and there is no reason to throw it in the trash. With a manual I could very likely cure the issues in an hour.
Trying to get a Tek service technician on the phone is like trying to dial up Presedent Bush. Pretty slim chance.
2 EchoWars:
Well, getting bush to the phone is now a lot easier because he is interested i nthe votes - so he will be easier to get for th common folks :
To the technician: Well, Ican only tell me experiences. In germany, only Cologne Tektronix main office is there (due to strategyi nthe market...). It usually takes me 5 to 10 minutes to get a technician. sometime I need a secound try to get a helpful one. I think this is not bad.
Of course avoid to get phones to the marketing areas -- you end up with a lot of new stuff information, but there is no help for the old equipment (well, no wonder).
Off course my posting is no way meant for you to throw it now i nthe trash. what I wanted to make clear: This cfg is designed to be send to trash if it is broken -- technician labour & parts is more expensive than a new cfg. Same with TDS210/220 scopes: If it's fried, the module change leaves you a bill near the price of a new instrument.
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Well, getting bush to the phone is now a lot easier because he is interested i nthe votes - so he will be easier to get for th common folks :
To the technician: Well, Ican only tell me experiences. In germany, only Cologne Tektronix main office is there (due to strategyi nthe market...). It usually takes me 5 to 10 minutes to get a technician. sometime I need a secound try to get a helpful one. I think this is not bad.
Of course avoid to get phones to the marketing areas -- you end up with a lot of new stuff information, but there is no help for the old equipment (well, no wonder).
Off course my posting is no way meant for you to throw it now i nthe trash. what I wanted to make clear: This cfg is designed to be send to trash if it is broken -- technician labour & parts is more expensive than a new cfg. Same with TDS210/220 scopes: If it's fried, the module change leaves you a bill near the price of a new instrument.
.
The problems you mentioned with the function generator are probably more than withing spec, except for the 50 mV offset. The sine wave is made from the triangle wave probably with a series of diodes. There are usually 1 - 3 pots for trimming the wave. The discontinuity at the top may be endemic, getting rid of it will be hard if even possible.
Is the 50 mV always there independent of the level setting? These usually have an output amp and there is an offset trim at the input of the amp. There will also be trims for the integrator, adjustments for the tracking of the panel/voltage to frequency conversion etc.
I would shop for a good Krohn Hite function generator before putting much energy into this one. You can get a KH 2200 lin/log 30 MHz generator for less than $100 on eBay. They can get below .1% THD with careful trimming (until the tem changes). The digitally synthesized generators are nice with very good specs, but expensive.
-Demian
Is the 50 mV always there independent of the level setting? These usually have an output amp and there is an offset trim at the input of the amp. There will also be trims for the integrator, adjustments for the tracking of the panel/voltage to frequency conversion etc.
I would shop for a good Krohn Hite function generator before putting much energy into this one. You can get a KH 2200 lin/log 30 MHz generator for less than $100 on eBay. They can get below .1% THD with careful trimming (until the tem changes). The digitally synthesized generators are nice with very good specs, but expensive.
-Demian
wondering about KH tuneable filters
there have been quite a few up for sale recently (I bought some from Kodak of all people) -- interesting that they have ganged precision pots and switchable capacitor banks -- sounds like a device in need of "repurposing" . fwiw, they seem to add a few 0.01% distortion to the output of my 1120 generator.
the SG505 (just got a manual) -- uses a dual 10K pot.
there have been quite a few up for sale recently (I bought some from Kodak of all people) -- interesting that they have ganged precision pots and switchable capacitor banks -- sounds like a device in need of "repurposing" . fwiw, they seem to add a few 0.01% distortion to the output of my 1120 generator.
the SG505 (just got a manual) -- uses a dual 10K pot.
The KH filters are very useful. They are not ultra low distortion (actually I think the VCVS filter has a limitation there) but they are otherwise very good. There are many models and different configurations. I have one that is battery powered (dead nicads after 20 yrs of course) but switch selected 48 dB/*ve filters that can be used independently or together and another that is adjustable slope and dials. And a few others. Good for testing speakers and subwoofers. I would be reluctant to use one for listening, but it may be real good.
The dual pot is part of a classic state variable oscillator. The same as the KH and the Boonton. The Boonton is electronically tuned and phase locked to a crystal reference making it in effect a synthesizer but with .0008% THD.
-Demian
The dual pot is part of a classic state variable oscillator. The same as the KH and the Boonton. The Boonton is electronically tuned and phase locked to a crystal reference making it in effect a synthesizer but with .0008% THD.
-Demian
CFG253
Interestingly enough, I was able to find an older gentleman who did contract work for Tek back in the day, and still has complete information on the unit, as well as his own adjustment procedures, worked out after repairing dozens of these things. He has promised me that he will get them copied and sent. Very cool.
Just as cool, my Tek SG505-02 arrived today! Looks like new, and cost me less than any eBay auction I've seen in a long time (<$250). Now, only if the power supply would show up.
Interestingly enough, I was able to find an older gentleman who did contract work for Tek back in the day, and still has complete information on the unit, as well as his own adjustment procedures, worked out after repairing dozens of these things. He has promised me that he will get them copied and sent. Very cool.
Just as cool, my Tek SG505-02 arrived today!
Looks like new, and cost me less than any eBay auction I've seen in a long time (<$250). Now, only if the power supply would show up.
go to Linear Technology's website -- they have an oscillator which uses two gain stages so you don't overdrive them. unfortunately they have changed the "look" of their website so it is missing some of the former functionality.
also http://www.amplifier.cd/Technische_Berichte/Amplifier_reiner_Sinus/amplifier_clean_sine.htm
i can also scan the SG505 schematic --
also http://www.amplifier.cd/Technische_Berichte/Amplifier_reiner_Sinus/amplifier_clean_sine.htm
i can also scan the SG505 schematic --
Go to http://www.linear-tech.com/ and do a search for AN43. The oscillator section begins on page 27.
The lowest distortion one they show (Fig. 48, THD of 0.0003%) has a range of only 1.5KHz to 15KHz. A couple of problems with building it:
1. You would need to provide switching of two film caps in the circuit (C1 and C2) from 0.1µf to 1µf, and that would give you two ranges...150Hz - 1.5KHz, and 1.5KHz - 15KHz.
2. Adjusting frequency with a standard potentiometer will be very very touchy. You would need a precision 10-turn dual potentiometer with very good channel-to-channel tracking. Not too hard to find, but they are NOT cheap.
3. The optical photocell might be a PITA to find. The Clarex CLM410 seems to be out of production, but the looks like the VTL5C10 is still made by PerkinElmer. I don't know who's backside you'd have to kiss to latch onto one of these devices, but it might not be hopeless.
4. The output of the circuit swings almost rail-to-rail by default. You would need another pot and likely an output buffer to make it really usable.
I was ready to go this route until I found the SG505 for a good price.
Edit: jackinnj, very cool!! Never saw that before. However, it's not exactly simple, and fixed at 10KHz freq. Still, unbelieveably low distortion. (it's AN67, BTW)
The lowest distortion one they show (Fig. 48, THD of 0.0003%) has a range of only 1.5KHz to 15KHz. A couple of problems with building it:
1. You would need to provide switching of two film caps in the circuit (C1 and C2) from 0.1µf to 1µf, and that would give you two ranges...150Hz - 1.5KHz, and 1.5KHz - 15KHz.
2. Adjusting frequency with a standard potentiometer will be very very touchy. You would need a precision 10-turn dual potentiometer with very good channel-to-channel tracking. Not too hard to find, but they are NOT cheap.
3. The optical photocell might be a PITA to find. The Clarex CLM410 seems to be out of production, but the looks like the VTL5C10 is still made by PerkinElmer. I don't know who's backside you'd have to kiss to latch onto one of these devices, but it might not be hopeless.
4. The output of the circuit swings almost rail-to-rail by default. You would need another pot and likely an output buffer to make it really usable.
I was ready to go this route until I found the SG505 for a good price.
Edit: jackinnj, very cool!! Never saw that before. However, it's not exactly simple, and fixed at 10KHz freq. Still, unbelieveably low distortion.
(it's AN67, BTW)