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Type G plugin versions
cmjones01
For a while I've been looking for a differential amplifier plugin for my 535A scope. While I really want a Z, W or 1A5, I couldn't resist a type G plugin at a great price locally. It was missing a knob and one valve but otherwise in great shape.
While getting it working, I've found that it's very different from what's documented in the manual available on TekWiki for the 53/54G. My plugin contains four 12AU6s, two 6AK5s and a 12AT7, as do the ones in the photos on TekWiki. The schematic in the manual, however, has two 12AU6s and three 12AT7s. The front panels are the same, though. http://w140.com/tekwiki/wiki/G What's going on here? Were there two versions of the plugin? I'd like to find the right manual for the plugin I've got. Thanks Chris
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Re: Type G plugin versions
Jerry Ingordo
Hi Chris.
You have an early G plugin. Here is a link to the early manual. http://ebaman.com/index.php/remository/func-startdown/22331/ You have to log in to download the manual. Log in is simple, create a screen name and password and your in. There may be a waiting period for new users to download. If you have a problem getting the manual contact me and I'll get a copy to you. Jerry W2JI
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Re: Type G plugin versions
cmjones01
Jerry,
Thank you very much for the pointer. That manual matches what I've got. A replacement 12AU6 (most of the vacuum has escaped from one of the ones in the plugin) has just arrived so I'll see if I can get it working. Regards Chris
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Re: 475 Probe Calibration problem with x10 probes
ef804s tubes
I have two 475 scopes. Both have developed a similar probe calibration problem on one channel. I am using the scope calibration signal. I have verified results with multiple probes
First scope - Channel 1 probe calibration tests fine with x1 and x10 probles. Channel 2 calibration tests fine with a x1 probe but the waveform has a sloped rise and fall time when testing with a x10 probe on a vertical sensitivity setting of .5v/div and above. Second scope - Channel 1 probe calibration tests fine with x1 probes but the waveform is a spike when testing with a x10 probe with vertical sensitivity setting of .5v/div and above. Channel 2 probe calibration works fine with x1 and x10 probes. Has anyone seen this problem? Mike N2MS Hi, please clean the attenuator contacts ans the pins of the attenuator blocks as well. Fred
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Re: 475 Probe Calibration problem with x10 probes
Colin Herbert
This might indeed help, but be cautious when doing it. There are posts on this forum where the correct technique is laid out - it is very easy to damage the cam-operated contacts. Also, note that the material of the attenuator board is a bit special and is easily damaged by heat and various solvents. Briefly, the technique is to put a little IPA (isopropyl alcohol) onto a sliver of ordinary paper and use that to clean the contacts. Check that the contacts are open, slide the ipa-wetted paper between them, close the contacts and then carefully pull the paper out level with the board, as far as possible. This can be done a few times to get all the contaminants off. You can probably ascertain which of the attenuator contacts need cleaning by checking in the service manual as to which attenuators are in circuit when the poor bandwidth is seen.
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Good Luck, Colin.
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of ef804s tubes Sent: 24 October 2018 14:27 To: TekScopes@groups.io Subject: Re: [TekScopes] 475 Probe Calibration problem with x10 probes I have two 475 scopes. Both have developed a similar probe calibration problem on one channel. I am using the scope calibration signal. I have verified results with multiple probes First scope - Channel 1 probe calibration tests fine with x1 and x10 probles. Channel 2 calibration tests fine with a x1 probe but the waveform has a sloped rise and fall time when testing with a x10 probe on a vertical sensitivity setting of .5v/div and above. Second scope - Channel 1 probe calibration tests fine with x1 probes but the waveform is a spike when testing with a x10 probe with vertical sensitivity setting of .5v/div and above. Channel 2 probe calibration works fine with x1 and x10 probes. Has anyone seen this problem? Mike N2MS Hi, please clean the attenuator contacts ans the pins of the attenuator blocks as well. Fred
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Re: Type G plugin versions
Dave Wise
Chris's manual is for the 53G (12AU6x2, 12AT7x2, 12AT7), while his plugin is the later, faster G (6AK5x2, 12AU6x2, 12AU6x2, 12AT7). I edited the wiki page to mention that 53G has five tubes while G has seven.
Regards, Dave Wise ________________________________________ From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jerry Ingordo <gjingordo@...> Sent: Wednesday, October 24, 2018 3:59 AM To: TekScopes@groups.io Subject: Re: [TekScopes] Type G plugin versions Hi Chris. You have an early G plugin. Here is a link to the early manual. http://ebaman.com/index.php/remository/func-startdown/22331/ You have to log in to download the manual. Log in is simple, create a screen name and password and your in. There may be a waiting period for new users to download. If you have a problem getting the manual contact me and I'll get a copy to you. Jerry W2JI
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Re: Type G plugin versions
Dave Seiter
My G (serial number just under 10K) has holes in the front panel for the original connectors, but is loaded with BNCs which look factory installed. Anyone know when this transition took place?
-Dave From: Dave Wise <david_wise@...> To: "TekScopes@groups.io" <TekScopes@groups.io> Sent: Wednesday, October 24, 2018 7:32 AM Subject: Re: [TekScopes] Type G plugin versions Chris's manual is for the 53G (12AU6x2, 12AT7x2, 12AT7), while his plugin is the later, faster G (6AK5x2, 12AU6x2, 12AU6x2, 12AT7). I edited the wiki page to mention that 53G has five tubes while G has seven. Regards, Dave Wise ________________________________________ From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jerry Ingordo <gjingordo@...> Sent: Wednesday, October 24, 2018 3:59 AM To: TekScopes@groups.io Subject: Re: [TekScopes] Type G plugin versions Hi Chris. You have an early G plugin. Here is a link to the early manual. http://ebaman.com/index.php/remository/func-startdown/22331/ You have to log in to download the manual. Log in is simple, create a screen name and password and your in. There may be a waiting period for new users to download. If you have a problem getting the manual contact me and I'll get a copy to you. Jerry W2JI
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Re: 475 Probe Calibration problem with x10 probes
n2msqrp
Thanks. Has anyone tried Caig Labs Deoxit?
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Mike N2MS
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Re: 475 Probe Calibration problem with x10 probes
n2msqrp Second scope - Channel 1 probe calibration tests fine with x1 probes but the >waveform is a spike when testing with a x10 probe with vertical sensitivity setting of >.5v/div and above. Channel 2 probe calibration works fine with x1 and x10 probes.(quote doesn't seem to work so I put the little arrows in like Usenet, hope it is clear enough) Unless those switches are dirty at many ranges or something it is not really likely they need to be cleaned and that is it. Therefore, troubleshooting is in order. A look at the front end on the print tells that in .5V/div and up the X100 attenuator is switched in the circuit. It is bypassed at the more sensitive rages. I assume here that when you wrote "and up" you meant higher in V/div. because "sensitivity" could be expressed the other way, more sensitive being <V/div. Also note that the X100 is the first in line so is most prone to damage by ridiculously high voltages. (that can happen when they DO NOT LISTEN ! - KEEP IT IN 10X AT ALL TIMES UNLESS YOU REALLY NEED THE GAIN. Better to fry the 9 meg or whatever resistance in the probe than the front end of the scope. The print does not give details on the internal of the attenuators, and with further examination I find that they are a unit, encapsulated and everything. I'm sure you'll find plenty in the hen's teeth department. As such, I say most likely there is a resistor in there that is blown open. I also say that most likely it simply goes from the input to the output. Its value should be calculable using the resistance of the output of the attenuator to common. (ground) Maybe 99X that measured value ? What it is not saying is if all these attenuators are in one package. All but the X10 show no connection to common. (ground) This is more than unlikely so I suspect there is simply an attenuation "block" of sorts. You'll have to determine which pins need the resistor. Either that or replace it/them. If there are separate ones for each channel at least you can make one good scope out of the pair. If there is only one for both channels you are up the creek. Actually it occurs to me now that you HAVE a good channel, a precision ohmmeter will tell you the value of resistor you would need to jump it out in the bad channel. You'll have to build that no doubt, unless you know where to buy like a 9.04256 megohm or whatever it is. Be mindful of RF/EMI, keep the leads short and straight as possible.
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Re: Type G plugin versions
cmjones01
On Wed, Oct 24, 2018 at 06:16 AM, cmjones01 wrote:
Thank you very much for the pointer. That manual matches what I've got. AReplacement 12AU6 installed in addition to a substitute for the missing 6AK5, adjustments to gain, DC balance and vertical position range as expected, plugin now seems to work perfectly. That wasn't too hard! Chris
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Re: Type G plugin versions
cmjones01
On Wed, Oct 24, 2018 at 10:21 AM, Dave Seiter wrote:
My G (serial number just under 10K) has holes in the front panel for theMy G also has BNC connectors. If it's anything like the other 500 series equipment, I think the transition was in the mid-to-late 1960s. My 535A has factory-fitted BNCs as well. Chris
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Anyone have a 5.5 to 18PF variable ceramic trimmer they would like to sell
Brendan
I ordered a 4 to 34PF from jameco but I would like another option. I just tapped it and I lost the trace on the 468 I'm working on. Good news is I found a dead transistor on the timing board. Now I have to wait on a trimmer to see if it fixes my issue.
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Re: Anyone have a 5.5 to 18PF variable ceramic trimmer they would like to sell
Can you send me a pic of the trimmer you need and how much room is there to mount it?
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73 Bill, WA2DVU
-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of lop pol via Groups.Io Sent: Wednesday, October 24, 2018 7:23 PM To: TekScopes@groups.io Subject: [TekScopes] Anyone have a 5.5 to 18PF variable ceramic trimmer they would like to sell I ordered a 4 to 34PF from jameco but I would like another option. I just tapped it and I lost the trace on the 468 I'm working on. Good news is I found a dead transistor on the timing board. Now I have to wait on a trimmer to see if it fixes my issue.
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Re: 2247A PSU Troubleshooting
tekscopegroup@...
Hi Nick, can't really give you other troubleshooting tips for a dead 2247A power supply, as I fortunately never had this problem with my own scope, but I hope in the end its something easy to fix. Maybe one of the 22xx series experts here would have some useful tips for you. You mention that you have the schematic, not sure if you actually have the complete service manual as well. If not I would strongly suggest to download a copy which just in case is available on the right hand column on this page:
http://w140.com/tekwiki/wiki/2247 Good luck with the troubleshooting, and don't forget to (hopefully) keep it fun. Also, please report back any progress so the information might possibly be useful for the next person having to go through the same scenario as you are now. Alex
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Re: TEK 475 Q1478 2n5859
It is not critical.
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Re: Anyone have a 5.5 to 18PF variable ceramic trimmer they would like to sell
Brendan
On Wed, Oct 24, 2018 at 05:57 PM, Bill Riches wrote:
I added a photo of the capacitor. Just in case. https://groups.io/g/TekScopes/photo/76822/0?p=Name,,,20,1,0,0
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Re: Anyone have a 5.5 to 18PF variable ceramic trimmer they would like to sell
I run into the same problem many times when restoring radios.
The original trimmers are simply not available So, I order new modern SMD trimmers from Mouser, and simply solder legs onto them. Works just fine. Menahem
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Re: 2247A PSU Troubleshooting
Nick,
I have a 2246A that I had to overhaul, which most likely has the identical power supply for your 2247A. I would do a search for the 2246A power supply also here. So I will refer to the component number in your schematic if there is a difference. I wouldn't be concerned with the diodes and caps mentioned in Alex's post until you verify the following. I also blew up U2201 when I accidentally shorted my scope probe shield against a heatsink while probing. That caused a no power on the main 44VDC bus measured at C2203. even if that is good, I would get a spare replacement. they are not expensive and still available as of a couple years ago. Get the service manual, refer to page 97, or 3-59, the power supply block diagram, and verify the voltage indicated prior to the preregulator and startup circuit at c2202. that is the main DC bus that feeds the Switching power supply pre-regulator. If you are plugged into 120VAC, it should be at about 160-170VDC. then switch meter to AC, and see if there is any ripple there. That's 120 hz so any meter will work. If that is good then check the previous paragraph for the 44VDC check. I also was able to test my power supply out of the cabinet. It was risky, but necessary. I used a 10KV AC rated linemans glove and placed the CRT lead inside of it. I also have the resistor values that were close loads for the power supply to operate at a typical load. NielsenTelecom
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Re: Type G plugin versions
Dave Wise
I don't know the G serial number at which Tek switched from UHF to BNC*, but the 1962 catalog shows UHF while 1963 is BNC**. I think I have a newer manual at home, I'll try to remember to look.
There was a mod kit for converting instruments in the field. I have at least one modded scope and plugin. Yours too, most likely, as Tek would not have sold instruments with such an obvious bodge. Dave Wise * For what it's worth, the 535A mainframe switched at 31260. ** Some old models were not updated. ________________________________________ From: TekScopes@groups.io <TekScopes@groups.io> on behalf of cmjones01 <chris@...> Sent: Wednesday, October 24, 2018 11:59 AM To: TekScopes@groups.io Subject: Re: [TekScopes] Type G plugin versions On Wed, Oct 24, 2018 at 10:21 AM, Dave Seiter wrote: My G (serial number just under 10K) has holes in the front panel for theMy G also has BNC connectors. If it's anything like the other 500 series equipment, I think the transition was in the mid-to-late 1960s. My 535A has factory-fitted BNCs as well. Chris
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Re: Type G plugin versions
Albert Otten
According to the later manual Type G switched from UHF (131-012) to BNC (131-277) at S/N 9480. No idea in which year that was.
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Albert
On Thu, Oct 25, 2018 at 08:17 PM, Dave Wise wrote:
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