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Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.


BTW: is it possible to get email notification only for dedicated topics?


--- In TekScopes@..., jerry massengale <j_massengale@> wrote:

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.


Jerry Massengale





-----Original Message-----
From: max_3289 <max_3289@>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed





Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?

not yet; have not known it yet.

Max.

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.


Jerry Massengale





-----Original Message-----
From: max_3289 <max_3289@...>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed





Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?

not yet; have not known it yet.

Max.

Hello Bob and Patrick,
Of course, what I really should have asked is if I should be worried about the internal temperature because the fan seems to run at full speed all the time and still there's no obvious airflow (detectable outside), although there's no obstruction. I have measured the voltage at the red feedthrough capacitor as around 12VDC.
From your comments, I tend to conclude that there's no need to worry. While calibrating the 'scope a few weeks ago, I had an external fan blowing air over the hybrids in very low volume at a very low speed, hardly more than a draft. It was enough to keep all hybrids almost as cool as the environment, whereas e.g. U600 heats up to at least 50C (untouchable) in still air. So, together with your comments, I've answered my own question I guess.

Thanks again for your input!

Raymond

--- In TekScopes@..., "Patrick Wong" <patwong3@> wrote:

Hi Raymond,

I own a 2465A and 2467. At least with those models, there is only one fan speed as there is no thermostatic control. I do not think the fans are very noisy and the amount of air flow is not tremendous.

I suggest that you remove the rear plastic cover and measure the voltage from the feedthrough capacitor located in the upper left corner (when viewing the rear) to ground. Note that the fan receives DC power via that capacitor.

You should find this voltage is constant. If you agree that the voltage is constant, yet the fan speed varies, then the fan needs help (perhaps cleaning) or replacement.

Good luck,

Patrick Wong AK6C

--- In TekScopes@..., "raymonddompfrank" <r.domp.frank@> wrote:

Hi,
The following has been sort of haunting me for a while:

When I switch on my 2445B, the fan starts running at a low speed and is barely
audible. After a while, it increases its speed to what I consider its maximum.
It is quite audible by then.

I have been trying for sometime to make a curve tracer adapter that can test all 5 transistors in the CA3046 array used in 7K series mainframes and plugins. I have been fighting a problem of oscillations in the gain curves. I was reluctant to add base resistors as gain would be affected. After trying several cures I find that it is necessary to use 560ohms in series with the base of the UUT. Is this acceptable?


Jerry Massengale

Mark,
If you don't already have the service manual, get it from KO4BB.com:

<<>>

I would assume the problem has something to do with channel switching, which is shown on the "Vertical Preamap & Output Ampl" diagram. The "foldouts lg" pdf seems to have the best scan of that circuit.
Try exercising the various vertical mode switches to make sure it isn't just dirty contacts. See if the various combinations of "CH1 BOTH CH2" and "ADD ALT CHOP" make sense in some positons and not in others--that my give you some clues.

--John Gord

--- In TekScopes@..., "Mark" <mjurras@> wrote:

My Tek 2235 has a problem, The input signal on Ch1 also is displayed by Ch2. This occurs whenever CH2 is displayed (Both or CH2 only) . It occurs even if Ch2 input is set to DC, GND or AC. When I adjust the vertical position of CH1, Ch2 moves. If I put the input on Ch2, Ch1 is not affected.

Can anyone help me troubleshoot this?

Hi Raymond,

I own a 2465A and 2467. At least with those models, there is only one fan speed as there is no thermostatic control. I do not think the fans are very noisy and the amount of air flow is not tremendous.

I suggest that you remove the rear plastic cover and measure the voltage from the feedthrough capacitor located in the upper left corner (when viewing the rear) to ground. Note that the fan receives DC power via that capacitor.

You should find this voltage is constant. If you agree that the voltage is constant, yet the fan speed varies, then the fan needs help (perhaps cleaning) or replacement.

Good luck,

Patrick Wong AK6C

--- In TekScopes@..., "raymonddompfrank" <r.domp.frank@> wrote:

Hi,
The following has been sort of haunting me for a while:

When I switch on my 2445B, the fan starts running at a low speed and is barely
audible. After a while, it increases its speed to what I consider its maximum.
It is quite audible by then.

The fan control circuit in all these model variations have a thermistor to vary the fan speed as the internal temperature increases. The outgoing airflow is mainly directed out the right rear corner, when viewed from the front of the instrument. Air flow on all the 24x5x instruments is critical, or certain hybrids will overheat to destruction. The TDS420 and related scopes do not have temperature control, while the 465 series does, but the fan is indeed quieter. The 7904 does not have a fan, but the 7904A does.



________________________________
From: raymonddompfrank <r.domp.frank@...>
To: TekScopes@...
Sent: Saturday, July 21, 2012 2:00 PM
Subject: [TekScopes] 244B internal temperature


??
Hi,
The following has been sort of haunting me for a while:

When I switch on my 2445B, the fan starts running at a low speed and is barely audible. After a while, it increases its speed to what I consider its maximum. It is quite audible by then. At the same time, I detect no air flow. Using a piece of tissue as an airflow detector I can't "prove" there's any air flow, apart from the fan's location at the back. Inside the 'scope, nothing is impeding the air flow. This seems independent of ambient temperature, which varies between 18C and 25C. The fact that I can't detect an airflow as such does't give me much concern, since often it's just a little "moving air" that's enough but i'd like to know if this is normal behaviour.
Can anyone of you confirm that it is normal for these 'scopes' (24x5y's) fans to be running at or close to maximum speed under normal operating conditions?
FYI, I'd like to add that I'm sure it's not noisy bearings or anything like that.
AAMOF, my TDS420 is even noisier, having a much larger fan as well.
My 465B isn't anywhere near as noisy, let alone my 7904 (which has no fan).

I'd appreciate to hear about anybody else's experiences.

Raymond

Hakan,

The ones I have on hand I believe were from a TDS540. The shield is one large die casting that attaches to the board. The shield presses 2 black plastic carriers that hold some sort of fuzzy metal ended pogo pins to contact the pcb at one end and each substrate at the other end.

Den



--- In TekScopes@..., "Hakan H" <hahi@> wrote:

--- In TekScopes@..., "baltimora86" <acuffe@> wrote:

I have a TDS784D where all four ceramic attenuator hybrids are cracked. I'm looking for replacements, and would like to know if any other models use compatible attenuators. Would the attenuators from a TDS744A work (even partially so I can check the rest of the scope)?

If anyone knows where I might be able to find them at a reasonable cost, I would love to hear from you. I'll take one with SPC problems since I know I can replace the relays.
----------------------

As far as I know all TDS's with the attenuator housing attached to the
Acq board use the same type of attenuators. However there are a whole
lot of versions used and I can't say what the differences are, possibly
bandwidth may be one. The ones with separate attenuator housing, e.g.
TDS520/540/544A etc. won't fit.
/H?kan

--- In TekScopes@..., "baltimora86" <acuffe@> wrote:

I have a TDS784D where all four ceramic attenuator hybrids are cracked. I'm looking for replacements, and would like to know if any other models use compatible attenuators. Would the attenuators from a TDS744A work (even partially so I can check the rest of the scope)?

If anyone knows where I might be able to find them at a reasonable cost, I would love to hear from you. I'll take one with SPC problems since I know I can replace the relays.
----------------------

As far as I know all TDS's with the attenuator housing attached to the
Acq board use the same type of attenuators. However there are a whole
lot of versions used and I can't say what the differences are, possibly
bandwidth may be one. The ones with separate attenuator housing, e.g.
TDS520/540/544A etc. won't fit.
/H?kan

My Tek 2235 has a problem, The input signal on Ch1 also is displayed by Ch2. This occurs whenever CH2 is displayed (Both or CH2 only) . It occurs even if Ch2 input is set to DC, GND or AC. When I adjust the vertical position of CH1, Ch2 moves. If I put the input on Ch2, Ch1 is not affected.

Can anyone help me troubleshoot this?

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

There used to be machined contact plugs (Augat, others) that had small diameter pins on both top and bottom of the green plastic substrate. I believe the pins were small enough to plug into a socket.

Actually, you could get single row strips of such pins now. Just find them at Samtec and request samples. Samtec is awesome and is quick (a few days for samples). I use them in many production products.

Den

--- In TekScopes@..., KeepIt SimpleStupid <keepitsimplestupid@> wrote:

Would this help:??

A dissolveable IC socket.?? I do remember seeing somewhere a carrier of sorts that has just the pins. So, you can solder either side and then remove the carrier.

In this case, you could put the socket on an IC,?? dissolve it away.?? Solder on either side and remove the IC.?? You could then use the item pictured, I think.

--- On Sat, 7/21/12, lilacbarn <lilacbarn@> wrote:

From: lilacbarn <lilacbarn@>
Subject: [TekScopes] Re: OT: Component sought
To: TekScopes@...
Date: Saturday, July 21, 2012, 10:40 PM
















??













--- In TekScopes@..., "David C. Partridge" <david.partridge@> wrote:

What I am looking for is something to allow a single sided PCB to be plugged into a DIL IC socket and have the tracks on the lower side.

The following links look almost right, but AFAICT they can only work on a DS PCB with plated holes (I just want to use single sided 0.1" strip-board for this).

<>

<>

I'm sure something suitable must exist ...

Thanks

Dave

Dave, have you got any old wire wrap IC sockets? I have used them in the past for exactly this purpose, but I have to be careful which type of DIL socket I use on the MB as the pins are square for wire wrap and bigger than a standard IC pin. I solder them to the daughter board but leave the full length of pin to push into the MB socket. It is a fixed height above the MB.

Geoff.

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?

not yet; have not known it yet.

Max.

Would this help:??

A dissolveable IC socket.?? I do remember seeing somewhere a carrier of sorts that has just the pins. So, you can solder either side and then remove the carrier.

In this case, you could put the socket on an IC,?? dissolve it away.?? Solder on either side and remove the IC.?? You could then use the item pictured, I think.

--- On Sat, 7/21/12, lilacbarn <lilacbarn@...> wrote:

From: lilacbarn <lilacbarn@...>
Subject: [TekScopes] Re: OT: Component sought
To: TekScopes@...
Date: Saturday, July 21, 2012, 10:40 PM
















??













--- In TekScopes@..., "David C. Partridge" <david.partridge@> wrote:

What I am looking for is something to allow a single sided PCB to be plugged into a DIL IC socket and have the tracks on the lower side.

The following links look almost right, but AFAICT they can only work on a DS PCB with plated holes (I just want to use single sided 0.1" strip-board for this).

<>

<>

I'm sure something suitable must exist ...

Thanks

Dave

Dave, have you got any old wire wrap IC sockets? I have used them in the past for exactly this purpose, but I have to be careful which type of DIL socket I use on the MB as the pins are square for wire wrap and bigger than a standard IC pin. I solder them to the daughter board but leave the full length of pin to push into the MB socket. It is a fixed height above the MB.

Geoff.