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Re: smd precision resistor "paint layer" peeled off while soldering *** advice needed ***
Ed Breya
If the over-coating on these SMDs has floated or burned off, then it's likely due to being undercut by the corrosive, leaked electrolyte. This stuff can travel considerable distance by capillary action on the surfaces. From your description of the resistors affected, they are fairly high precision, metal film types. The paint flaking off indicates the metal films have been compromised by the corrosion, so may be out of spec - they would tend to be higher in resistance due to missing some of the metal. Try to measure the values in-circuit, as accurately as possible, considering the associated circuitry.
If you get everything properly cleaned up and working again, you can measure the operating voltages in that section, and assess whether the resistors are still OK. If good, just leave them alone. Ed
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Re: 7A26 edge distortion
On Wed, Oct 21, 2020 at 02:49 PM, Raymond Domp Frank wrote:
The problem was indeed caused by defective trimcaps: I started by replacing 4 (four !) open trimcaps in Ch2, made preliminary adjustments and took another picture. See album. I'd never have thought that practically (?) all trimcaps of the problem-type would be defective in the one unit but then again, it *is* a systemic problem. Thanks to John and Roger for your help and suggestions! Raymond
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
adesilva_1999@...
I understand and I figured out what made me think otherwise. It is the generic picture of a multiplier they have on the semiconductor manual at the top of that page! Lesson learnt.
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Re: 067-0912-00 needed
Clark Foley
Dennis,
Did you ever make duplicates of that early 7804N conversion board (K7-1286-XA)? Clark
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Re: 577D1 Phantom base current
DW,
My "ZERO Line trace" stays flat, right against the bottom of the CRT graticule. When testing a transistor with the steps set to 1, I see two lines, the first is that "zero line trace" at the very bottom of the CRT and when increasing the collector voltage this line always moves straight across from left to right, with no perceptible vertical deflection. The next line or trace would be the single trace that you would expect to get. As the collector voltage knob is increased, that trace moves left and up from the corner of the graticule, as one would expect. Of course, this is indicating increased voltage as well as the presence of current. The ZERO line is always present , representing the collector voltage knob position, regardless of the number of steps selected, except when the collector voltage knob is set to zero; when it becomes a single dot. Hope this answers your question. -- Michael Lynch Dardanelle, AR
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Re: 577D1 Phantom base current
DW
Michael,
Thanks for the reply. From what you observed I am not getting the same results. The phenomenon I am experiencing seems to be an issue with improper biasing on the base terminal. When you set the set the step generator to the single setting, do you notice when raising the collector voltage there appears to be current increase initially then levels off horizontally across the display. And when setting the step amplitude higher or lower this will affect how how much vertical deflection until the line goes horizontal again. Or does it just stay flat at 0. I hope this makes sense.
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Re: 067-0912-00 needed
Dave Daniel
A schematic for the -00 version of the board is in the datasheet link on the TekWiki page to which Dennis pointed.
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DaveD
On Oct 21, 2020, at 13:45, Dennis Tillman W7pF <dennis@ridesoft.com> wrote:
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Re: 067-0912-00 needed
Hi Eric,
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I can't help with a schematic, but there is some information on this card on TekWiki at http://w140.com/tekwiki/wiki/067-0912-00 Dennis Tillman W7pF
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric Sent: Wednesday, October 21, 2020 8:55 AM To: TekScopes@groups.io Subject: [TekScopes] 067-0912-00 needed I am thinking about trying to tackle a calibration on my 7854. I have confirmed that the digital and analog sections are out of adjustment. The digital section is about .8 division left of center. In looking through the calibration document It seems I have everything I need to do the calibration except the 067-0912-00 the analog test board. How likely is this something that I am going to be able to acquire it does not look too complex from the schematic just a few IC’s and a data bus. -- Dennis Tillman W7pF TekScopes Moderator
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067-0912-00 needed
Eric
I am thinking about trying to tackle a calibration on my 7854. I have confirmed that the digital and analog sections are out of adjustment. The digital section is about .8 division left of center. In looking through the calibration document It seems I have everything I need to do the calibration except the 067-0912-00 the analog test board. How likely is this something that I am going to be able to acquire it does not look too complex from the schematic just a few IC’s and a data bus.
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
On Tue, Oct 20, 2020 at 11:20 PM, <adesilva_1999@yahoo.com> wrote:
They did not use the same part number for two different parts. The 455 and 465M both use the U550 designation in their schematics, both use the identical TEK part # 152-0635-00. 152-0635-00 is the "all in one" HV Multiplier along with other circuitry. The 465(not "M)/465B/475 , on the other hand, use the 152-0552-01, which is the stand alone "6 stage" Multiplier, not usable in the 455/465M. This series of scopes has the other circuitry externally, on the main board. Much easier to fix, but less manufacturing friendly. -- Michael Lynch Dardanelle, AR
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Re: smd precision resistor "paint layer" peeled off while soldering *** advice needed ***
Thanks Chuck
73 Richard W4MCD
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Re: 7A26 edge distortion
On Wed, Oct 21, 2020 at 04:20 AM, Raymond Domp Frank wrote:
This is my newest 7A26 (main PCB code 670-2549-21)! S/N 709928, so Heerenveen. It's the only one in my collection with a green PCB and 155-0078's with date code "429", I guess that's 8429. Raymond
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Re: 7A26 edge distortion
On Wed, Oct 21, 2020 at 07:52 AM, Roger Evans wrote:
Hi Roger, Since these components constitute most of the common parts, I had done some testing in that area. I checked Vbe across Q820 / Q840, Q860 / Q880 and they were correct. I pulled Q860 and Q880 and lifted one end of CR860. No difference. Next, I bridged some of the trimmer caps with small fixed caps each at a time and found a significant influence. I'm going to check and replace trimmer caps! Raymond
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Re: 7A26 edge distortion
On Wed, Oct 21, 2020 at 06:55 AM, John Gord wrote:
Hi John, I know the problem with the trimmer caps. I found several that had no effect, initially blaming that on the lack of HF content in the signal as it appears and not expecting a multi-device failure. I temporarily put some small caps (3 - 10 pF) in parallel with one trimmer-cap at a time and so far, I've found 5 (yes, five) that immediately made the pulse steeper, without overdoing it, in both channels! I'm afraid this is going to exhaust my donor supply... Raymond
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Re: 7A26 edge distortion
On Wed, Oct 21, 2020 at 06:27 AM, John Gord wrote:
Hi John, Both edges show the same behavior. Raymond
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Re: Nice 556 still available for free but pickup only
Chris J
Omit, previous message as I see your title, plainly states, "available for free".... Still waking up, here. Good price for a hobbyist with little to spare. Best email is Cjuried@yahoo.com and phone is 954-478-4355
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Sincerely, Chris https://juriedengineering.com/ FCC Licensed RF Coordinator Audio Engineering Society (AES) Member This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any distribution or copying of this email, and any attachments thereto, is strictly prohibited. If you have received this email in error, please immediately notify me at (954) 478-4355 and permanently delete the original and any copy of any e-mail and any printout thereof.
On Tuesday, October 20, 2020, 10:53:14 PM EDT, Grayson Evans <wa4gvm@gmail.com> wrote:
Hi Chris, You are welcome to come pick it up. Ft. Lauderdale to here is about an hour and 15 maybe 30 I think. If you are interested, send me an email and I will send you an address. Grayson
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Re: Nice 556 still available for free but pickup only
Chris J
Sure. Cjuried@yahoo.com how much are you a asking?
Chris Juried, WRCB719 FCC Licensed RF Coordinator Audio Engineering Society (AES) Member InfoComm-Recognized AV Technologist http://www.JuriedEngineering.com http://www.HistoryOfRecording.com http://www.linkedin.com/in/chrisjuried Email: CJuried@yahoo.com Voice: (954) 478-4355 This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any distribution or copying of this email, and any attachments thereto, is strictly prohibited. If you have received this email in error, please immediately notify me at (954) 478-4355 and permanently delete the original and any copy of any e-mail and any printout thereof. On Tue, Oct 20, 2020 at 10:53 PM, Grayson Evans<wa4gvm@gmail.com> wrote: Hi Chris, You are welcome to come pick it up. Ft. Lauderdale to here is about an hour and 15 maybe 30 I think. If you are interested, send me an email and I will send you an address. Grayson
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Re: Tek 2430A collapsed screen image
Tom Lee
Hi Szabolcs,
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By any chance, are you related at all to the violinist Joseph Szigeti? --Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu
On 10/21/2020 02:01, Szabolcs Szigeti wrote:
Hi,
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Re: Tek 2430A collapsed screen image
Szabolcs Szigeti
Hi,
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This could be a lot of things. But the first thing is to check the power supplies. If you don't have the service manual, first get it from for example TekWiki: http://w140.com/tekwiki/wiki/2430 Check all the power rails for proper voltage and ripple. If they are not good, chances are that you have bad caps in the PSU, common for this model r have a shorted cap on one of the boards. Also check the interconnecting cables between the boards. These are the checks I would do first. Szabolcs <jwdtek@charter.net> ezt írta (időpont: 2020. okt. 21., Sze, 6:39):
Does anyone know what can cause the screen image to collapse and only show
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Re: High-Risk Ceramic Strip Locations in Types 535/545
tek_547
Thanx for the info David. I had the same experience with trace intensity variations on a 547.
After several hours searching and measuring it was a voltage variation on the grid of V800, and so increasing the HT. Inspecting of the ceramic strips around I saw a kind of black sooting at the solder joints so time to clean them all with IPA. After that the voltage around V800 was stable and also the intensity, so happy at all that it was not the HV transformer. I think it must be that after warming up the scope the sooting gets conductive wich give voltage variations at the grid of V800. grtz and stay safe, René
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