Re: Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book
Dear Dennis, we are fortunate to have the chance to buy this book.
I Understand completely the issues in PayPal.
I notice that the email for the PayPal account seems to be an organization. If it received many payments marked "friends and family" the PayPal robots may raise a red flag.
IDEA.... you could offer an alternative payment to PayPal:
eg the buyer posts to you or Peter a check ( only for buying by USA not overseas)
Just a name and address needed, NO PayPal holding, fees or commercial vs friends questions.
I am gladly going to send the $37, but I await your response, as I prefer to post a check.
DENNIS THANKS FOR ALL YOUR KIND WORK OVER THE YEARS!
from A very grateful TEK afficanado ( since 1970!)
Jon
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Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.
The prices are more than I'm willing to pay, but there are a bunch of mechanical keyboard whackos out there inflating the prices for this kind of stuff. The market will do what the market does, whether the motives of the participants is in any way rational.
I also suspect that there is a large element of supply & demand at work: for lots of reasons this kind of equipment is becoming rarer and rarer, and that's simply got to drive the price up if there is any kind of demand. The prices would certainly have been a lot lower a decade or two ago, but those days are gone. You might also be able to find some of these things at a hamfest for lower prices, if you can find a hamfest to go to (I haven't seen a hamfest in my area in many years), but even there you are likely to see increasing scarcity of older equipment.
Finally, my impression is that IBM equipment generally didn't make its way into private hands, both because these systems were marketed almost exclusively to corporate and institutional buyers, and because IBM preferred to lease equipment rather than sell it outright. This had the effect of radically restricting the aftermarket on such things, which is reflected in current scarcities. You'll have similar difficulty finding systems from other manufacturers in the same space (e.g. Burroughs, Honeywell, Univac, Sperry, etc.).
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If changing R160 didn't have any effect, then are the +15 VDC and -15 VDC present at its two ends? Did adjusting both R160s not do anything on either channel? I suppose it is possible that something drastic has happened to both baluns (T1301 on both channels), if someone accidentally fed in too much voltage on both channels, but I would have thought that Q150A/Q150B would have died first.
A resistance of 56R between the centre of the BNC input and the non-earthy end of R130 looks to be correct - it is R10.
You might have dirty AC/GND/DC switches - these contacts are a bit prone to getting a bit mucky after years of service, but they should only be cleaned with isopropanol and carefully. It is easy to bend the gold-plated leaves if you are too aggressive and the board substrate can be damaged by other solvents. I have cleaned attenuator cam-switches, but not the AC/GND/DC switches. Others may give you advice on that. You may also have dirt on the attenuator switches, but time will tell.
You may well have faulty Q150s, but since they are dual FETs in the two channels, I would have though the failure of all four devices was a little unlikely.
I don't think that dirty attenuator switches would give the symptoms you describe, but I could be wrong, I often am. Dirt on these switch contacts usually has an effect on the frequency response of the affected attenuator, the dirt being capacitative. It's a pity that both channels are exhibiting the same fault, because otherwise you could swap components like the individual attenuator units and the Q150s between the two.
I have had a problem (still do, to some extent) with one of my 7A26s in that one channel was showing a different gain to the other. I think I got near to sorting that out by replacing the faulty U1350, but my memory is a bit hazy - not that that helps with your problem.
I am assuming that you have the appropriate Service Manual (you are quoting part-numbers) and that you have checked all of the voltage rails. That is often a cause of faults.
Good Luck, they are nice amplifiers,
Colin.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Jouko Koskinen Sent: 25 November 2020 14:38 To: [email protected]Subject: Re: [TekScopes] 7A26 no signal Thanks for the replies, R160 didn't have any effect on the trace. I think the problem might be in the attenuator/source follower part Attenuator in 10mV/div setting. Resistance from BNC to R130 shows 56R. Probe in place and connected to calibrator I can't see any signal in R130. Input resistance from BNC is only 340k. When I remove Q150 it is 1M as it should be. Situation is similar in both inputs. Q150 damaged in both inputs??? I suppose the attenuator switches can't make this behaviour? Regards, Jouko
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Re: Choosing the right replacement cap
BTW, Newark is having a 15% off black Friday sale now. Just got an email.
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Re: Choosing the right replacement cap
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Re: 2710 Spectrum Analyser 'Cannot count VCO, IF' error
Hi all,
Nice to meet you.
Just after answering I saw all the other responces. Sorry for not having checked further developments in time.
Jaap
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Re: Choosing the right replacement cap
Hey adesilva_1999, please feel free to email me directly to discuss any 465 questions. We seem to be on the same path. Have you taken out the vertical preamp yet? Message me if not. I learned a few things taking it out that were not at all obvious for a first timer like myself.
Dave
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Re: To pay for Peter Keller's Book ...
On Wed, Nov 25, 2020 at 12:53 PM Lawrance A. Schneider < llaassllaaass@...> wrote: To pay with PayPal, it need more than MarianT@... . I don't know what
the "..." is. Clearly, I'm lesserly smart than others, but I just don't
know what to use.
It looks like the web interface on groups.io garbles anything that looks like an email address. I don't have trouble with this in email delivery, see /g/TekScopes/message/173743.
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Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.
Those prices are not reasonable, and the sellers do not accept offers,
contrary to what's advertised on eBay.
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On Wed, Nov 25, 2020 at 4:57 PM Jeff Dutky <jeff.dutky@...> wrote: A quick look at ePay reveals 3 IBM 5110s, and two 5120s all asking in
excess of $1200 (all but one are OBO, so you might be able to get a
discount). Shipping on these things is going to be bear, however. There are
lots of watchers on each one.
The 5120 is especially interesting looking, with a larger display, two
vertically mounted 8 inch floppies, and a generally "rounder" look to the
case: the thing just screams 1975. If I had any interest in these machines
I might be tempted to pick one up.
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Re: 2710 Spectrum Analyser 'Cannot count VCO, IF' error
Hello Martin,
Sorry for the late responce. I have an open 2712 here which had repairs and now need adjustments. I checked the signals you asked for:
J195 - signal comes from the Reference Board and was as it should be a stable in amplitude 100MHz signal about 300mV peak-peak, which is about calculated -7dBm.
J190 - 10MHz signal, more or less square wave 450mV peak-peak, which is about 0dBm calculated (including harmonics).
J180 - I measured while "in LOCK" state (in the 2712 lower than in 50kHz/div spans) a constant 800mV peak-peak 16MHz - while not "in LOCK" state there were signal bursts while changing the span/div.
I hope this helps you a bit further. I will have this and other of this family analyzers open for a while to come, so it will be easy for me to do measurements.
Jaap PA0JRK
Netherlands
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Re: Choosing the right replacement cap
On 2020-11-25 12:59 p.m., Dave Peterson via groups.io wrote: Thanks everyone for the endorsements on these component suppliers. Makes me feel good about joining in, and you have given me some good ideas on how to order - like accumulating a shopping list and ordering when it's over a certain value. That's what I do, to hit Digikey's free shipping threshold. That way I can fool myself that I'm saving money! --Toby
...
Dave
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Re: Choosing the right replacement cap
Yep, C1534: 3uF 55v supply filter cap (continuity to TP1536). At least it's not a signal cap (too large anyway?).
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Re: Choosing the right replacement cap
adesilva_1999,
Is C1534 the "can" at the back of A9 that's near VR1525?!
I just unmounted the + lead yesterday to check it because it had the same "white flaky stuff". I almost dove into a full tear down of dismounting A9 because of it. Cooler heads prevailed and the pulling of the + lead allowed me to check it (it was good) and get it soldered back in. Looks way better anyway.
I hadn't gotten to checking it's existence in the schematics yet.
I'd say "white flaky stuff" isn't a problem in-and-of-itself, but I would like to know what's going on there.
Dave
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Re: Fix or Part Out a Tek 475A
oops I meant the 1N400x series....I was interrupted while typing and hit send prior proofing...you are correct.
oh the leads on 160 were same as 4148
¸é±ð²Ô¨¦±ð
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On 11/25/20 10:32 AM, Jeff Dutky wrote: ¸é±ð²Ô¨¦±ð,
what I used to replace the same is MUR 160 ... the 4148 was not fast enough But the datasheet for the MUR160 gives Trr of 60 ns, while the 1N4148 gives Trr of 4 ns. How could the 1N4148 be too slow?
Also the capacitance of the MUR160 is 20 pF compared to the 1N4148's 4 pF, so the MUR160 would throw the capacitance of the whole sub-circuit off.
Finally, when I look at alleged pictures of MUR160s they seem to have really fat leads, which makes sense given their higher current rating, but that will only make it more difficult to place them in the existing holes, especially since I'm having to do the rework without access to the backside of the PCB.
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Re: Choosing the right replacement cap
Thanks to Dave and the rest who are on this thread. I am trying to restore a low serial 465 as I write. I also got good pointers from EEV blog. Some great contributors there. Some of you may be on there also. I will book mark this and if I can, I will make some comments.
That C 1419 is a common failure from what I have read. Someone also pointed to the "wet tantalum" caps like C 1534. I just found this last night as the + ve lead was surrounded by white flaky stuff where it goes in to the board. Surprisingly, it shows no leakage near the cap itself! Now I have to check for similar caps elsewhere.
My scope works for the most part except the CH 2. Some positions seem to have bad contact on those flimsy switch contacts. Before I go into the caps, I want to get that sorted out.
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Re: Fix or Part Out a Tek 475A
¸é±ð²Ô¨¦±ð, what I used to replace the same is MUR 160 ... the 4148 was not fast enough But the datasheet for the MUR160 gives Trr of 60 ns, while the 1N4148 gives Trr of 4 ns. How could the 1N4148 be too slow? Also the capacitance of the MUR160 is 20 pF compared to the 1N4148's 4 pF, so the MUR160 would throw the capacitance of the whole sub-circuit off. Finally, when I look at alleged pictures of MUR160s they seem to have really fat leads, which makes sense given their higher current rating, but that will only make it more difficult to place them in the existing holes, especially since I'm having to do the rework without access to the backside of the PCB.
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Tektronix 492A input attenuator repair ????
Hello Groupe
I have this 492A spectrum analyzer and I have found that the input attenuator (0-60DB) i defect.... is it still possible to get spare parts for this attenuator
or is there a better way to repair it ....
I have bypass the attenuator and I can se signal on the display, so I hope that the rest of the spectrum analyzer is working...
OZ1CT Ben
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My rule of thumb when looking at electronic equipment on E-bay or anywhere else is to look *closely* for signs that anyone has been into it. If it isn't *sealed* and it's not guaranteed to work then expect the worst. I wouldn't pay more than a *minimal* price for anything that has been opened and that isn't guaranteed to operate properly. I've seen far too much equipment for sale by big time used equipment dealers such as Tucker Electronics being sold in "as-is" condition that I'm sure have already been stripped of anything useful. On Wed, Nov 25, 2020 at 10:08 AM David Holland <david.w.holland@...> wrote: Yeah, as Brenda said....
The manuals detail what vacuum tubes are in the plugins. I'd pay close
attention to any photos as I've gotten burnt once or twice by not paying
attention to them. I would presume if there's no photos, and no statement
one way or the other, that the tubes are missing.
If you start getting into the advanced (sampling) plugins, I would pay
closer attention to the photos for the presence of the transistors, as most
of them are socketed, long obsolete, and made from 99.95% pure unobtanium.
A few plugins (ex: 3B3) use tunnel diodes, but as far as I've seen, they're
generally soldered to the board. Tunnel diodes are also mostly made of
unobtanium, and may be dead, but at least they'll likely still be there...
:-)
Again, the various plugin manuals all have a relatively complete parts list
in the back, if you wonder what should be in a given plugin.
David
On Tue, Nov 24, 2020 at 12:05 PM Brenda via groups.io <brendda75=
[email protected]> wrote:
Hello Dave, The 3A1 plugins that I have come across ends up not only the
6DJ8 tubes missing, there are 2 8233 tubes that end up missing as well.
There are 4 7586 nuvistor tubes in the front end, but seems like the tube
pickers pass over these from my experience. I am in the market for a few
3A1 and 3A6 plugins myself...at a reasonable price, $400 is just way too
much!!
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Re: Choosing the right replacement cap
AGREED,
We use Mouser primarily, they have a fulfillment center at Love Field (or is it DFW?)so shipping response is great. Having said that we also us Allied, Newark, and Digikey with similar results. Arrow is OK IF you can figure out their website and they have minimums.
All of these folks have shipped one part orders without question. Here in the US, Mouser has a $7.99 shipping charge for up to 2-day so that¡¯s a help also.
Steve
Datagate Systems, LLC
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of toby@... Sent: Wednesday, November 25, 2020 8:47 AM To: [email protected]Subject: Re: [TekScopes] Choosing the right replacement cap On 2020-11-25 11:11 a.m., Tom Phillips wrote: Dave,
Regarding your question "How are places like Mouser and Digikey with small time onsie-twosie buyers..."
I have found that they are amazingly cooperative with small orders. I have been refurbishing many of my personal test equipment units each of which need a variety of replacement electrolytic caps. I end up ordering "kits" of parts after spending a significant amount of time using the search engines on the supplier's web site to find high quality replacements of suitable size and value. I choose only "in stock" parts because the stated manufacturers lead time for non stocked parts is just an estimate and usually requires a substantial minimum order quantity. I also want my "kit" to arrive complete so I can get on with the project. During my last order I found that Mouser didn't quite have all the parts I needed but Newark did and the Newark pricing was better. Digikey is a good supplier too. I just haven't needed to use them recently. +1. I use Digikey constantly, they will ship a single part just as efficiently as 10,000. I've had (free) deliveries of tiny orders within 11 hours of ordering. Just a happy customer. --T
Tom
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I know some of you guys deal with older computers and PCMCIA cards so I figured I'd offer it up here first.
I have an ISA bus PC Card adapter (card that goes into the ISA bus and you can plug a PC Card card into it). I don't know if it'll take one card or two, it's new and sealed. Made by or for Lucent/Orinoco.
Second item is a Lucent/Orinoco PC Card wireless network adapter 11Mbps. Also new and sealed.
I have no use for either and before I bit bucket or recycle it, I figured I would offer it up here for the cost of shipping. CONUS only.
You can email me direct at either:
vev at michvhf dot com OR vev at cdupe dot com
Vince - K8ZW.
--
K8ZW
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Jean-Paul
Dave Peterson