开云体育

Ed Breya via Groups.Io <edbreya@...> 於 2018年6月11日 上午12:58 寫道：

I picked up this 500 MHz SA for cheap, because the CRT display is very dim, although it appears to work otherwise. I was hoping that some internal adjustments would fix it right up, but no. The unit is labelled Atten Instruments, model AT5005, and appears to be a Chines knockoff of the Hameg HM5005 - or maybe they're all made in China anyway. I couldn't find a manual for it, but did find the one for Hameg 5010, which includes schematics and more. It looks like the basic units are the same, especially the PS and CRT circuits, so I have what I need to check it out eventually. This is low priority, but it could be a handy toy SA for limited field use and such - it's definitely more portable than the good old real SAs I'm used to.

Just wondering if anyone happens to be familiar with this unit and common problems with it, to maybe find a quick fix. I haven't made any of the usual internal checks yet. One thing I noticed is that the focus adjustment needs to be at one extreme for a sharp, but barely visible display. I'm guessing there's something wrong in the CRT HV circuits, rather than the CRT having gone bad - unless that's one of the common problems with these.

Ed

Hi David,
What type of capacitors do you suggest replacing the 575 paper caps with,
and where do you buy them?
Thank you to all that have contributed to this 575 topic!
tom jobe...

On 6/10/2018 3:17 PM, David Holland wrote:

There are a number of paper capacitors in the HV section. (Amongst other
locations). I'm sure folks will disagree, but I'd recommend preemptively
replacing them. (Any capacitor described as PTM in the parts list is
paper.)

Be careful with C809, if you decide to replace it, its soldered directly
across T801. The wires for the transformer, which will likely come out
with the capacitor, are (very) fine.

David

Obligatory: If anyone wants a non-Mod122C, and is in the Dayton Ohio
area,
and is willing to pick it up, holler. It has been restored, and was
running last I tried it. (No, I will not ship, sorry)

On Sun, Jun 10, 2018 at 5:23 PM, John <John@...> wrote:

Thanks for the advice guys: I do normally run stuff up on a variac, and I
will check those fuses are in place. Fortunately I have a supply of
many
of the valves used (and a valve-tester): fingers crossed it's not had all
the valves stripped!

John

There are a number of paper capacitors in the HV section. (Amongst other
locations). I'm sure folks will disagree, but I'd recommend preemptively
replacing them. (Any capacitor described as PTM in the parts list is
paper.)

Be careful with C809, if you decide to replace it, its soldered directly
across T801. The wires for the transformer, which will likely come out
with the capacitor, are (very) fine.

David

Obligatory: If anyone wants a non-Mod122C, and is in the Dayton Ohio area,
and is willing to pick it up, holler. It has been restored, and was
running last I tried it. (No, I will not ship, sorry)

On Sun, Jun 10, 2018 at 5:23 PM, John <John@...> wrote:

Thanks for the advice guys: I do normally run stuff up on a variac, and I
will check those fuses are in place. Fortunately I have a supply of many
of the valves used (and a valve-tester): fingers crossed it's not had all
the valves stripped!

John

Thanks for the advice guys: I do normally run stuff up on a variac, and I
will check those fuses are in place. Fortunately I have a supply of many
of the valves used (and a valve-tester): fingers crossed it's not had all
the valves stripped!

John

I believe you are asking for this:
/g/TekScopes/files/Caps%20list%20updated%20March%202018.xlsx

I've just bought (but not yet collected) a 575, I think the 400V option. I suspect it's been stored several years unused. This will be my first piece of Tek valve kit (apart from a 130). Is there an informaiton resource for 575's which gives pointers to particular isues/ problems etc? Am I likely to have any EHT transformer worries? etc. etc.
Many thanks
John

Thank you Albert. I put the scope in dc coupling and centered it. Needed to
adjust the scope to .5V/div in order to keep the same gain for comparison.

Here are the waveforms:

/g/TekScopes/photo/49286/9?p=Name,,,20,1,0,0

Collector is a hair more than emitter, base is a little more than twice the dc
bias, as you say about 0.65V.

Is that the correct way?

Keith

I spent some time going over the circuit around Q1416, and made a photo with
the various components labeled here:

/g/TekScopes/photo/49286/6?p=Name,,,20,1,0,0

in case someone sees that I've misidentified something.

I looked at the waveform at Q1416-collector as Albert suggested, and took this
photo:

/g/TekScopes/photo/49286/7?p=Name,,,20,1,0,0

But when I then also looked at the base and emitter, the waveforms are exactly
the same (!). I thought... uh.. probably means Q1416 is bad (despite being
tested good on a diode checker), so I hunted around and found a replacement
from my 464 (which also has a dead CRT circuit). Same results. Then I thought,
well... could be that one is bad as well, so I just put in another new
PN2222... and got the same results.

So, what's going on here? I had previously replaced C1419 with that small
electrolytic you see in the photo.

While I was at it I figured I better photo the waveforms at Q1418, here:

/g/TekScopes/photo/49286/8?p=Name,,,20,1,0,0

-----Original Message-----
From: John Sent: Sunday, June 10, 2018 9:04 AM

I've just bought (but not yet collected) a 575, I think the 400V
option. I suspect it's been stored several years unused. This will be
my first piece of Tek valve kit (apart from a 130). Is there an
informaiton resource for 575's which gives pointers to particular
isues/ problems etc? Am I likely to have any EHT transformer worries?
etc. etc.
Many thanks
John

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Dennis Tillman W7PF
Sent: Saturday, June 09, 2018 8:14 PM
To: [email protected]
Subject: Re: [TekScopes] Tek 7a13 mechanical to LED display conversion
? / 7ct1n user notes ?

Rick,

Download the 7D13 mechanical version manual and the 7D13 digital
version manual and look at the very first section of the manuals where
there is a detailed photograph with callouts that show where
everything is located on the front panel. Aside from the mechanical
readout and it's knob everything else is exactly the same and in the
same place. Vc Out is in the same place on both versions also.

Then read the section on First time use to learn how to set the 7A13
up. The only thing you might want to change is to set the + input to
DC, ground the - input, Set the bandwidth to 5MHz, set the Volts/Div
knob to 50mV/Div and un-calibrate the vertical Volts/Div. Last thing
is to connect the 7CT1N wire to the + input of the 7A13. That is all
you need except to read how to setup the 7CT1N for the particular
transistor or FET you will be testing. To test a FET you must reverse
the Drain and Gate leads as the plugin clearly shows under the banana
jacks.

Dennis Tillman W7PF

-----Original Message-----
From: hrgerson@... Sent: Saturday, June 09, 2018 7:44 PM
To: [email protected]

<snip>

" ... The plug-in can still be used when the counter fails, by using
an external voltmeter to monitor the comparison voltage, Vc."

- So, on the old version, where is Vc to 'tap' into