开云体育

If I had a 2245 with your problem I'd be looking for... Hmm. Your parts are running naked, right - no heat sink? That's maybe 1W.
An eBay seller has TO-92 VP0116 $15 for 10, glue on a copper fin. But nobody is selling VN1316 AFAICT.

Look at Mouser.com . They don't have any 160V P-channel RF MOSFETs so how about the regular ones? In 150V-300V select the lowest Ciss proxied as gate charge, that's Diodes Inc ZVP2545 in the SOT26-6 package. Put a copper fin on the drain pins and you should be okay.
For N-channel try Vishay SI3440 in TSOP-6. Second lowest gate charge and lowest Ciss.

HTH,
Dave Wise
________________________________
From: [email protected] <[email protected]> on behalf of Chris Elmquist via groups.io <chrise@...>
Sent: Wednesday, April 2, 2025 9:28 AM
To: [email protected] <[email protected]>
Subject: [TekScopes] horz output FETs in 2245?


I was given a 2245 recently which of course doesn't work too well.

Investigation reveals that Q805 and Q806, in the horizontal right plate
output stage, are cold to the touch.

The service manual, section 6.2 (page 6-19) says,

The MOSFET output transistors (Q801 and Q802 left plate-- Q805 and
Q806 right plate) run hot. If either side is cold, it is defective.

So, that's me and now I need to find a couple of these VDMOS FETs, which
seem to have become quite rare.

They are Tek P/N,

151-1211 VN1316N2 N-Channel VDMOS FET, 160V, 250mA, 40 ohm
151-1212 VP0116N2 P-Channel VDMOS FET, 160V, 250mA, 25 ohm

Has anyone solved this problem with a modern replacement pair? and have
suggested substitutes? These are in TO-39 package which adds additional
challenge but I suppose TO-220 or equiv could be made to fit. Of course,
the real thing would be great too if there is a source.

Thanks for any leads!

Chris
--
Chris Elmquist

On Wed, Apr 2, 2025 at 12:41?PM Raymond Domp Frank via groups.io <hewpatek=
[email protected]> wrote:

'm no expert on U800 failures, but the two videos I found show different
symptoms

I was triggered by the frequent symptom of the complete screen info
pulling to one side - and beyond. I hope it’s not that serious though.

Yeah, you may well be right. Aside from the power supplies and U800, I
can't think of much that's common to the OSD and traces in the horizontal.
Personally I like to look for simple, inexpensive and fixable problems
first, I guess it's a case of streetlight effect (
).

'm no expert on U800 failures, but the two videos I found show different
symptoms

I was triggered by the frequent symptom of the complete screen info pulling to one side - and beyond. I hope it’s not that serious though.
Raymond

I was given a 2245 recently which of course doesn't work too well.

Investigation reveals that Q805 and Q806, in the horizontal right plate
output stage, are cold to the touch.

The service manual, section 6.2 (page 6-19) says,

The MOSFET output transistors (Q801 and Q802 left plate-- Q805 and
Q806 right plate) run hot. If either side is cold, it is defective.

So, that's me and now I need to find a couple of these VDMOS FETs, which
seem to have become quite rare.

They are Tek P/N,

151-1211 VN1316N2 N-Channel VDMOS FET, 160V, 250mA, 40 ohm
151-1212 VP0116N2 P-Channel VDMOS FET, 160V, 250mA, 25 ohm

Has anyone solved this problem with a modern replacement pair? and have
suggested substitutes? These are in TO-39 package which adds additional
challenge but I suppose TO-220 or equiv could be made to fit. Of course,
the real thing would be great too if there is a source.

Thanks for any leads!

Chris
--
Chris Elmquist

Intensity is way too high IMHO, which is why you get that problem.

If OTOH you don't want your SC504s and are in the UK ...

D.

How do you know which manual is appropriate to the SN? Am I missing the obvious? I have manuals with the PN of 070-6863-00 and 070-6863-01

SN is B058926. it powers up normally and passes all self tests. It will complete (assumedly from the light sequences) the boot sequence and power on tests even when the display is wonky. It seems to be the focus is lost and the display position is just past the right edge of the screen. At first it appeared to possibly be temperature related but now not so much... it does it from a cold (well, at least cool) boot now and it started working *after* warmup one time prior. When the screen is not correct it seems to respond to all button presses - the fuzzy blobs move in concert with the presses although it is only what could be described as the left quarter of a fuzzy blob that shows on the right side of the CRT. Running the self test while also seems to complete it's entire sequence.

Hal

Greetings,

I have 2 SC504 scopes. I have done a lot of restoration work on both these units. They are both working now, but I am not satisfied with the trace having ghost. Please take a look at the photo I posted some days ago. At that time I had 1 SC504, since then I have bought another one. BOTH of these scopes display EXACTLY the same ghost trace.

When I bought the second SC504 I thought I would have the chance to swap out the CRTs.

/g/TekScopes/photo/300558/3883505?p=Created%2C%2C%2C20%2C2%2C0%2C0

Thanks for the responses.

Barrr

Hey Harold,

I'm no expert on U800 failures, but the two videos I found show different
symptoms: . While the trace is
affected, the on-screen-display is not in both of those cases. Of course we
don't know whether you've turned the OSD off on your scope, and there is
likely more than one failure mode for U800, so YMMV.
Does the scope successfully complete power up? If it's failing
power-on-self-tests, it'll stop at some point with a single front-panel LED
lit, and when you press A/B TRIG, it'll continue to operating mode, which
will click some relays.
After that, the first thing to look at is the power supplies at J119.
There's a table in the service manual that specifies limits on voltage and
ripple. The next thing to look at IMHO are the -1.25V and +1.36V references
on the A5 board. If any of those are out, there's no point in looking at
anything else.

From there it's a process of elimination, I'd say, and if you haven't read
this document: , maybe
that's a good start. It's a fun read, if nothing else.
Some things to try:
- Does the beamfinder do anything?
- Does the OSD show?
- Does X/Y mode work?
- Does the B-sweep work?
- Does the 10X horizontal magnify do anything?

Since the symptom is so severe, you should be able to quickly figure out
what is bad in the horizontal or the HV.

Good luck,
Siggi

On Wed, Apr 2, 2025 at 9:18?AM Harold Foster via groups.io <halfoster=
[email protected]> wrote:

That was the kind of thing that I was worried about. I do have a parts
unit so maybe that could be used if needed. I'm not sure when I will get
the chance to dig into it but I very much appreciate the ideas. I've not
worked on these before so at least knowing where to start reading up is
extremely helpful.

Thanks!

What SN? A5 SMD or TH ? Beware as hrs can be changes at CAL.

Have full serv man for the serial range?

Usual drill:

0/ IF A5 is SMD check for corroded SMD cap damages

1/ Check all PSU V/ripple at U119 header on A1 bd

2/ Probe CRT hor pins or HOR amp output for large DC bias.


Bon chance


Jon

That was the kind of thing that I was worried about. I do have a parts unit so maybe that could be used if needed. I'm not sure when I will get the chance to dig into it but I very much appreciate the ideas. I've not worked on these before so at least knowing where to start reading up is extremely helpful.

Thanks!

My thoughts are not so much about a HV problem as the infamous U800 horizontal driving chip.

Raymond

Harold,

It is likely that resistors on the high voltage board are bad. I did post the R numbers and other information for someone recently having focus problems.

Mark

I have a nice 2465B that I bought as being fully restored and recapped (I’ve not opened it up yet but have no reason to doubt) that only has about 460 hours on it. I bought it back at the end of the summer but have only put maybe an hour and a half on it since; I turned it on a couple of days ago and it had a perfect display then suddenly everything disappeared to a diffuse glow off the right side of the screen (UL to photo album "2465B screen issue") After about 5 minutes it snapped back to being correct and stayed that way for another 30 minutes until I turned it off. I turned it on yesterday and it worked perfectly for about 15 minutes then went back to the fuzzies and has not returned to normal yet. Note there is no gradual transition between states, it is as far as I could tell instantaneous. When the display was working it had a perfect, sharp image and passed all self-tests. The problem is obviously (???) in the CRT/display circuitry, but I have not opened it up yet to check anything – I was hoping to find someone that might be more familiar with these units prior to starting.

Any hints and advice are very much welcome.

I've temporarily owned such a system a few years ago. The pictures on Tekwiki show that system. But it's not that easy. On top you'll need a terminal and a compatible signature analyzer. And some components like the signature tables (and maybe the diagnostics ROM) have to be matched to the hardware revision of your 7854.

The diagnostics ROM board also contains some stand-alone diagnostics routines which are helpful for calibration and some digitizing problems.

I've uploaded the involved firmware roms and scans of the manuals to tekwiki. I think the vintageTEK museum is still selling a clone of the diagnostics ROM board.

But in my opinion it's way easier to diagnose the system "by hand".

Holger

The SG505 was designed by the founder of Audio Precision, Bruce Hofer. It
is a marvelous signal generator for audio with a THD% level approaching the
level of the SYS2722. For those interested there was an article in Audio
decades ago about a copy-cat version written by Bob Cordell on his website
cordellaudio.com. Jack

Sorry, nothing here like that

I looked for one of these a decade or so ago and didn't find anything.

DaveD
KC0WJN


On Tue, Apr 1, 2025 at 02:05 Alberto, IZ2EWV via groups.io <iz2ewv=
[email protected]> wrote:

Did I put a silly request? Nobody knows what I’m looking for or it’s
nowadays so rare that only museums and some collectors keep that equipment
closed inside a display case?
Thank you for you attention.
Alberto

Did I put a silly request? Nobody knows what I’m looking for or it’s nowadays so rare that only museums and some collectors keep that equipment closed inside a display case?
Thank you for you attention.
Alberto

Hi Tom,

Don't really remember how I did ut.

I followed a YouTube video where somebody demonstrated how to make round banners in Word, and took it from there.

Sorry,

Leo