Hi all,
with respect to FET's, I'd like to think of them as purely "Voltage" driven.
So, imho you're both making the same point:
If an one fet has a bigger input capacitance than the other, the drive circuit needs to be able to reach the required ON-voltage by delivering a higher current to charge the higher input capacitance of that FET.
If a FET need a higher input charge (nC) to switch on, that may be just the combination of ON-voltage and Input capacitance of that particular FET.
Basically: Q = C x V , Charge (Coulombs) = Capacitance (F) x Voltage (V)
The FET i ordered (IPA60R280E6) has a GS threshold voltage of 3-3,5V, so the 14V puse should be high enough to drive it, Voltage wise.
The original FET IRF710 has a GS threshold voltage of 4V.
I like the idea of running the chip by applying a test voltage of 28V down to 14V as used to test the chip as described in H?kan's document, and, while running, put a 1nF capacitor (imitating a worst case FET) in place of the real FET's G-S.
This way, using a second scope, I can see if the driver circuit is capable of driver this higher, capacitive load.
All this with Q9030 removed of course.
If not, I even may change (lower) R909 a bit.
A combination of R909 at 39Ohm and 200pF (original FET) would give an approximate risetime of 8ns;
A combination of R909 at 39Ohm and 1000pF (replacement FET) would give an approximate risetime of 40ns.
For now I ignore the ristime of Q908, the drive transistor in this comparison.
I will try the capacitor test later this afternoon.
Assume the switching frequency of the PS is 40kHz, thus having a period of 25us, so even with a dutycycle of 10% ON-pulses (ON-time 2,5us) the new risetime should work OK in terms of pulse duration.
The thing that might be a thingy could be the power consumption of the FET during the ON-OFF transitions, and for that reason it can be helped to increase the risetime by reducing R909 to force the FET to switch fully ON faster.
On the other hand, having a way lower ON-resistance could make up for the power consumption durig transistions
So far my thoughts, any ideas?
Un saludo,
Leo
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Re: Replacing Electrolytics in a 465/465B
Hello Barry,
Nice job and clean solution congrats. I have 2 x 465B and one 465 that need to be recap soon. I would love to get 3 boards. What is the price for them. Also I live in France did you accept international shipping? Also the related cost.
Please let me know.
Have a nice day.
Victor
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-----Original Message----- From: n4buq <n4buq@...> To: TekScopes < [email protected]> Sent: Wed, Jul 25, 2018 1:05 am Subject: [TekScopes] Replacing Electrolytics in a 465/465B Recently, I had a problem with the LV supplies in my 465B. Thinking it was a shorted electrolytic can, I decided to replace all of them (although it turned out to be a shorted tantalum but had already pulled the cans before finding the real problem). I decided to design a small PC board on which to mount modern snap-in caps. THe board mounts with standoffs in the exising larger holes that are left when the cans are removed and allow replacement of the snap-ins if/when they fail and that can be done without further soldering on the original board. Pictures of the board and the process are in the following album: /g/TekScopes/album?id=64929If anyone is interested, I have extra boards for sale. Thanks, Barry - N4BUQ
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Re: All TekScopes email sent to Spam
If you're using Yahoo mail to read messages, it's happening because you've hit the Spam button instead of Delete.? The button locations move, and it's easy to hit the spam button if you're not careful.? I do it about once every other week with some of my email.? Three times I've received a nastygram stating that I've been terminated from IO because of this, but there is always a link to rejoin the group in question if it was an error.? That's always worked, so far. -Dave From: Andre de guerin via Groups.Io <testing_h@...> To: [email protected] Sent: Wednesday, July 25, 2018 12:25 PM Subject: Re: [TekScopes] All TekScopes email sent to Spam Same here. Any ideas? www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened." ? ? On Wednesday, 25 July 2018, 19:36:02 GMT+1, Carl Hallberg via Groups.Io <n9ess@...> wrote: Help, Now all my TekScopes email is sent to spam folder.? Is this a Yahoo problem?? Carl Hallberg? (W9CJH)
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Just wanted to get a little clarity here and also do an update. Went through a number of the scopes I have now and have found three of them where the wet tant has already been replaced with aluminum electrolytics same one that is leaking on the 466 board I am working on. On one of them it was replaced with a 1000uf 10v and on another a 1000uf 35v was used they replaced a 1000uf 10v wet tant they are both larger but fit in place. There is no way to fit a three times capacitance increase in place for that one found a 3300uf 16v that is closest to it at 3 times. There is a very small wet one used on the 464/466 that is 3.6uf 125v that is leaking on the one board I can get a 10uf 160v to replace it think it will fit but would using a solid bulb type of tant same uf but higher voltage be a better choice?
Made a list of wet tants used and what aluminum lytics I could get to replace with and most are close for fitting there are three leakers on this board and one iffy.
Jim
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Re: Looking for Power Cord for 400-series Scope
Wasn't Tek using Belden power cords at that time?
Michael A. Terrell
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-----Original Message----- From: Phillip Potter <p.potter@...>
Sent: Jul 25, 2018 11:56 PM
To: [email protected]
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope
I wish to add my two cents...
I purchased some power cord to replace the butched one on my 453 (w/
same wire specs) only to find that it was too big (overall size) to fit
the cable clamp on the scope! I was forced to whittle the outside sheath
down to get it to fit... I was not happy but did end up with a cord that
included a plug with a cord holder.? I learned my lesson; never
assume... I know, I know!
Phil
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Re: Looking for Power Cord for 400-series Scope
I wish to add my two cents...
I purchased some power cord to replace the butched one on my 453 (w/ same wire specs) only to find that it was too big (overall size) to fit the cable clamp on the scope! I was forced to whittle the outside sheath down to get it to fit... I was not happy but did end up with a cord that included a plug with a cord holder.? I learned my lesson; never assume... I know, I know!
Phil
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On 7/25/2018 5:05 PM, n4buq wrote: Okay, Jim. I took a second look and the power entry section is just a small part of the back panel so that would be a fairly easy replacement.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Barry" <n4buq@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 11:14:21 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope
Okay - I'll take a look again at that. Perhaps it isn't as much trouble as I
was thinking it was.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jim Olson" <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 10:51:07 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope
The panel is easy to get off it is held on just two flat head phillips
screws
and the fuse cover box it lifts off with the cord attached you just need to
take off the wires the ground is bolted to the frame right at the cord in
and the white neutral wire is soldered to the fuse box and the power is
attached to a blue piece on the main board soldered too.
Jim
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Did you find a knob for your scope? I have some for different 4** series scopes how is the clear flange marked and does it have a black ring around the cal red knob?
Jim
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Re: WTB: v9.7 EPROMs for 495P memory board
Wow! You da man! Thanks!
RB
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Re: WTB: v9.7 EPROMs for 495P memory board
On Wed, 25 Jul 2018, Rick Boswell wrote: [Edited Message Follows]
Sergey,
Thanks for your detailed post. I am new to SA's in general and to the 495P
specifically but am learning. I have spent considerable time with the
two-volume service manual (700+ pages) as well as reviewing various online
resources such John Miles notes, the KO4BB website, and others. Some
responses & questions re your comments:
Firmware: I am familiar with the physical distribution of the firmware on
the A54 memory board, GPIB board, and front panel. Thanks for your offer
to provide images to allow me to program the EPROMs I am looking for. At
present, I don't have the devices or programmer to do this, and since my
need is almost certain to be a one-time need, I'd like to avoid
programming my own EPROMs if I can purchase what I need. I am also I can program and send you those 2 chips, no problems. Just send me your address off list to ksi at koi8 dot net. No need to pay anything assuming you are in the US so it would make it with domestic First Class package. I have lot of 27256 chips here and it takes just couple of minutes to program 2 chips. --- * * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * *
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Re: WTB: v9.7 EPROMs for 495P memory board
Sergey,
Thanks for your detailed post. I am new to SA's in general and to the 495P specifically but am learning. I have spent considerable time with the two-volume service manual (700+ pages) as well as reviewing various online resources such John Miles notes, the KO4BB website, and others. Some responses & questions re your comments:
Firmware: I am familiar with the physical distribution of the firmware on the A54 memory board, GPIB board, and front panel. Thanks for your offer to provide images to allow me to program the EPROMs I am looking for. At present, I don't have the devices or programmer to do this, and since my need is almost certain to be a one-time need, I'd like to avoid programming my own EPROMs if I can purchase what I need. I am also familiar with the front panel MCU. I own two 495Ps, one of which I purchased in essentially new condition and which works well. Along with this one I received a "parts" 495P which I find works as it should if I simply install a known good A54 memory board which has v9.7 EPROMs installed.. It boots up as a 495P, indicates v9.7 firmware is installed and v1.1 firmware on the front panel processor. So, it would seem that my issues are a result of a defective A54 memory board. I have obtained an A54 memory board from an older 494 unit with v9.0 firmware, and am looking for the v9.7 EPROMs to update this board. I have compared the 494 and 495 memory boards visually and via the parts lists and circuit diagrams in the service manuals and see no meaningful difference. I have moved the v9.7 EPROMs from a good A54 board to the 494 board and installed this in the non-working 495P and it works as expected.
Power supply: As far as I have investigated to date, the power supplies in both 495Ps are working as they should. IOW, I am able to step through the initial checkout section of the service manual and get the results specified in the manual. The capacitors have apparently not yet failed, or may have been replaced by previous owners. Since this has not been an issue yet, I haven't looked carefully to see if these might have been replaced. I see no anomalies in operation which would suggest a power supply problem, but I am still early in the checkout/repair process.
Fan: Not sure yet how to determine if the fan is working properly. For sure, It is turning and moving air. The top of the case gets mildly warm to the touch after several hours of operation, but this doesn't doesn't seem excessive given how much is going on inside this jam packed case. Is there a way to determine if the fan is working as designed? I know it is turning but don't know if it is moving the amount of air it was designed to do. The fan runs quietly, so no apparent mechanical issues.
Thanks,
Rick
K8EZB
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Re: All TekScopes email sent to Spam
Unless they're using a Yahoo email address..
Vince.
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On 07/25/2018 07:35 PM, David C. Partridge wrote: The mail isn't coming from yahoo any more guys, we moved to the groups.io server.
Dave
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Griessen
Sent: 25 July 2018 21:18
To: [email protected]
Subject: Re: [TekScopes] All TekScopes email sent to Spam
On 07/25/2018 02:36 PM, Harvey White wrote:
It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. Right. various yahoo.com servers may have been downgraded in their trustworthiness
and then the settings of your junk sensing flag it as junk. If you change settings to
allow from yahoo it will probably come through. That's called whitelisting.
No problem here using thunderbird email reader.
I also run my own mail server and it is not using the real time blacklisting
rankings of yahoo to reject mail from yahoo. Yahoo is still deemed trustworthy by them
as far as I can tell.
--
Michigan VHF Corp.
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Re: Looking for Power Cord for 400-series Scope
Okay, Jim. I took a second look and the power entry section is just a small part of the back panel so that would be a fairly easy replacement.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Barry" <n4buq@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 11:14:21 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope
Okay - I'll take a look again at that. Perhaps it isn't as much trouble as I
was thinking it was.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jim Olson" <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 10:51:07 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope
The panel is easy to get off it is held on just two flat head phillips
screws
and the fuse cover box it lifts off with the cord attached you just need to
take off the wires the ground is bolted to the frame right at the cord in
and the white neutral wire is soldered to the fuse box and the power is
attached to a blue piece on the main board soldered too.
Jim
|
Re: All TekScopes email sent to Spam
The mail isn't coming from yahoo any more guys, we moved to the groups.io server.
Dave
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of John Griessen Sent: 25 July 2018 21:18 To: [email protected]Subject: Re: [TekScopes] All TekScopes email sent to Spam On 07/25/2018 02:36 PM, Harvey White wrote: It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. Right. various yahoo.com servers may have been downgraded in their trustworthiness and then the settings of your junk sensing flag it as junk. If you change settings to allow from yahoo it will probably come through. That's called whitelisting. No problem here using thunderbird email reader. I also run my own mail server and it is not using the real time blacklisting rankings of yahoo to reject mail from yahoo. Yahoo is still deemed trustworthy by them as far as I can tell.
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Re: All TekScopes email sent to Spam
On Wed, Jul 25, 2018 at 11:35 AM, Carl Hallberg wrote:
Help,
Now all my TekScopes email is sent to spam folder. Is this a Yahoo problem?
Carl Hallberg (W9CJH)
Same issue here. Marked them as not spam and all is fine now.
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Re: Tek 495P A54 Memory Board Repair
Chipquick is definitely very useful when the project calls for it.
JK
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of stefan_trethan Sent: Wednesday, July 25, 2018 4:36 PM To: [email protected]Subject: Re: [TekScopes] Tek 495P A54 Memory Board Repair If anyone is having trouble with replacing components, maybe try Chipquick low temperature alloy. Recently I came into an obscene hoard of that stuff, and found that it works rather well. I don't really use it, I have the tools and practice to replace anything I work with (the other day I exchanged a transformer over 50 times on the same board!), but that low melting alloy makes it really easy, even without any special tools. I would still recommend that you get the tools and skills to do this the old fashioned way, but if you are worried about damaging some expensive piece of kit then this Chipquick stuff might just steady your hand. A colleague has even used gallium to swap parts without any soldering at all. Not so useful for repairs, but it was a pretty neat trick as long as you didn't jostle the board. Funny metal, that, especially if you put some on aluminium. ST
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Re: WTB: v9.7 EPROMs for 495P memory board
On Wed, 25 Jul 2018, Rick Boswell wrote: Want to buy 495P v9.7 EPROMs which are installed on the A54 memory board.
P/Ns 160-8316-00 and 160-8315-00. There are 9 EPROMs in v9.7 firmware in 494AP that should be the same as you have. They are part numbers 160-8315-00 to 160-8323-00. First 2 are on that memory board, rest is on GPIB board. I have all firmware images and can send 'em to you so you would be able to program your own chips. There is another thing -- it is _NOT_ just those switches that tell the firmware what instrument it runs on. There is also another MCU on the front panel that runs its own firmware. Main instrument firmware asks the front panel MCU about hardware version and that is taken into consideration when deciding what hardware it runs on. For example, 494AP and 2756P have EXACTLY SAME switches configuration and main firmware decides what it runs on based on what front panel controller told. 494AP and 2756P are identical inside just case and front panel is different. 2756P has full-blown 494AP chassis inside sans front panel and its own front panel. Part of the case not occupied by 494AP chassis is simply empty. If you remove that chassis and install a 494AP front panel on it the thing will tell you it is 494AP and will happily run as 494AP without flipping a single switch. And BTW, did you replace _ALL_ electrolytic caps in the power supply except those 2 big ones protruding through its cover? If you didn't start with this first -- it is almost 100% probability that most (if not all) of those capacitors are dead and your instrument just acts erratically. There is absolutely no reason to even start doing anything on any part of the instrument until you have the power supply refurbished. You should also make sure the fan is working properly -- unlike some other instruments in 49x it is CRITICAL. If it doesn't work your PS will overheat in almost no time. --- * * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * *
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Re: All TekScopes email sent to Spam
Uh, aren't we on groups.io now rather than yahoo?? Yahoo is out of the picture.
Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: John Griessen <john@...> Date: 7/25/18 1:17 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] All TekScopes email sent to Spam On 07/25/2018 02:36 PM, Harvey White wrote: ?? It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. Right.? various yahoo.com servers may have been downgraded in their trustworthiness and then the settings of your junk sensing flag it as junk.? If you change settings to allow from yahoo it will probably come through.? That's called whitelisting. No problem here using thunderbird email reader. I also run my own mail server and it is not using the real time blacklisting rankings of yahoo to reject mail from yahoo.? Yahoo is still deemed trustworthy by them as far as I can tell.
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Re: All TekScopes email sent to Spam
I thought our group was using "groups.io" not Yahoo.? Yahoo should not be involved unless they are your email client.? I use Yahoo email client and web based email.? That Yahoo client dumped all of my messages to SPAM one day last week.? But I marked them as "Not Spam" and everything has be good since then.
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Show quoted text
On ?Wednesday?, ?July? ?25?, ?2018? ?03?:?18?:?04? ?PM? ?CDT, John Griessen <john@...> wrote: On 07/25/2018 02:36 PM, Harvey White wrote: ? It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. Right.? various yahoo.com servers may have been downgraded in their trustworthiness and then the settings of your junk sensing flag it as junk.? If you change settings to allow from yahoo it will probably come through.? That's called whitelisting. No problem here using thunderbird email reader. I also run my own mail server and it is not using the real time blacklisting rankings of yahoo to reject mail from yahoo.? Yahoo is still deemed trustworthy by them as far as I can tell.
|
Re: Tek 495P A54 Memory Board Repair
If anyone is having trouble with replacing components, maybe try
Chipquick low temperature alloy.
Recently I came into an obscene hoard of that stuff, and found that it
works rather well.
I don't really use it, I have the tools and practice to replace
anything I work with (the other day I exchanged a transformer over 50
times on the same board!), but that low melting alloy makes it really
easy, even without any special tools.
I would still recommend that you get the tools and skills to do this
the old fashioned way, but if you are worried about damaging some
expensive piece of kit then this Chipquick stuff might just steady
your hand.
A colleague has even used gallium to swap parts without any soldering
at all. Not so useful for repairs, but it was a pretty neat trick as
long as you didn't jostle the board. Funny metal, that, especially if
you put some on aluminium.
ST
|
Re: All TekScopes email sent to Spam
On 07/25/2018 02:36 PM, Harvey White wrote: It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. Right. various yahoo.com servers may have been downgraded in their trustworthiness and then the settings of your junk sensing flag it as junk. If you change settings to allow from yahoo it will probably come through. That's called whitelisting. No problem here using thunderbird email reader. I also run my own mail server and it is not using the real time blacklisting rankings of yahoo to reject mail from yahoo. Yahoo is still deemed trustworthy by them as far as I can tell.
|
satbeginner
Victor
Michael A. Terrell
Sergey Kubushyn
David C. Partridge