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Does no-one really have any observations on this?
Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Colin Herbert via Groups.Io
Sent: 17 March 2019 13:43
To: [email protected]
Subject: [TekScopes] TM504 backplane repair

I have a TM504 where contact B22 on the high-power compartment connector has got mangled. It can be seen that it is sitting badly and maybe shorting to A22. I know that this connector isn't used very frequently, but I was hoping to use my PS503A in that compartment to take advantage of the 1A output. I have obtained a brand-new connector (#131-1078-00) and was hoping to be able to use it to effect a repair. I think I have a number of options:

a) Unsolder the entire faulty connector and replace it with the new one - this looks like a formidable task, since there are a total of 56 pins to unsolder and re-solder and access isn't straightforward but it would be the most ideal option, I think. Unfortunately I don't have a de-soldering tool, only a solder-sucker and some poor de-soldering braid (I suppose I could buy a de-soldering tool).

b) Somehow remove the faulty contact and replace it with a good one from the new connector. This would be fine, but it doesn't look easy because of the way the contacts are secured in the new connector, they are not easy to remove as they are retained by way of a punched indentation which has resulted in a raised "dot" on the other side. I have tried crushing this down, but it isn't easy. If the mangled contact in the existing connector is retained in the same manner, I can't see how removal can be managed.

c) Just remove the mangled contact by "brute force and ignorance" and forget about its function for the PS503A (it is -V output) . This wouldn't be ideal but would probably be functional, even though it would irritate me as being imperfect.

d) disconnect the electrical connection to the faulty contact on the TM504. I don't like this idea at all.

e) disconnect the electrical contact on the PS503A. I like this option even less than (d).

Does anyone have any experience of doing such a repair or any other/better ideas?

TIA, Colin.

The 2465B has a separate CURSOR 0 line, but DLY REF 1 is shared. I think
this was done to allow cursors under delay sweeps. I'd guess DLY REF 0
controls the B-sweep timing, so I'd take a gander in your shoes.

On Thu, Mar 21, 2019 at 11:07 AM <thespin@...> wrote:

DLY REF 0/1 also control the position of the vertical cursors, right?
These function just fine, so I don't think it's these control lines.

On Thu, Mar 21, 2019 at 10:13 AM, Siggi wrote:

On Thu, Mar 21, 2019 at 9:48 AM Chuck Harris <cfharris@...> wrote:

4051 MUX's fail regularly, as do the opamps in the sample and hold
cells... and be suspicious of any CA3046's, or 3346's. on
occasion one of the sample and hold storage capacitors will get
leaky.

I also remember a case where a decoupling capacitor on the mainboard side
of one of the A5 control lines went leaky and pulled the control signal
down.

DLY REF 0/1 also control the position of the vertical cursors, right?
These function just fine, so I don't think it's these control lines.

On Thu, Mar 21, 2019 at 10:13 AM, Siggi wrote:

On Thu, Mar 21, 2019 at 9:48 AM Chuck Harris <cfharris@...> wrote:

4051 MUX's fail regularly, as do the opamps in the sample and hold
cells... and be suspicious of any CA3046's, or 3346's. on
occasion one of the sample and hold storage capacitors will get
leaky.

I also remember a case where a decoupling capacitor on the mainboard side
of one of the A5 control lines went leaky and pulled the control signal
down.

On Thu, Mar 21, 2019 at 9:48 AM Chuck Harris <cfharris@...> wrote:

4051 MUX's fail regularly, as do the opamps in the sample and hold
cells... and be suspicious of any CA3046's, or 3346's. on
occasion one of the sample and hold storage capacitors will get
leaky.

I also remember a case where a decoupling capacitor on the mainboard side
of one of the A5 control lines went leaky and pulled the control signal
down.

Pulling the relevant cables and adding the jumpers didn’t seem to help. Will proceed by measuring all the relevant triggering lines and trying to figure out what’s holding the sweep back from happening. But nobody has seen this sort of problem where there’s no B sweep and assigned blame to one of the hybrids or the display sequencer or one of the surrounding components?

On Wed, Mar 20, 2019 at 07:44 AM, Chuck Harris wrote:

Was this the 2465B that had the CTS installed? If so, pull all the
plugs, and install jumpers on J102, pins 3&4, 1&7, and J101 pins 1&3, 6&8.

The sweep won't work if those paths aren't connected... for whatever reason.

-Chuck Harris

Pulling the relevant cables and adding the jumpers didn’t seem to help.
Will proceed by measuring all the relevant triggering lines and trying to
figure out what’s holding the sweep back from happening. But nobody has
seen this sort of problem where there’s no B sweep and assigned blame to
one of the hybrids or the display sequencer or one of the surrounding
components?

On Wed, Mar 20, 2019 at 07:44 AM, Chuck Harris wrote:

Was this the 2465B that had the CTS installed? If so, pull all the
plugs, and install jumpers on J102, pins 3&4, 1&7, and J101 pins 1&3,

6&8.

The sweep won't work if those paths aren't connected... for whatever

reason.

-Chuck Harris

Siggi wrote:

I’d look at the A5 timing reference signals next. Those go to DR of

U700

and get compared with the ramp voltage to gate the B sweep. On the A5

board

they’re DLY REF 0/1.

NB: did you try dual delay sweeps? I believe that mode will use only

the A

sweep, but alternate the delay between the two control voltages,

allowing

you to see whether the controls are responsive.

On Tue, Mar 19, 2019 at 19:56 <thespin@...> wrote:

1. No sweeps seem to work
2. The opamp outputs look close enough that I'm inclined to assume

they're

doing their job
3. THO on U900 appears stuck high for all front panel configurations I
could test. It dips low momentarily when turning the sec/div knob, but
shows no periodic behavior.

On Tue, Mar 19, 2019 at 07:20 PM, <thespin@...> wrote:

I've tried cleaning U500 and U900 to no avail, and then I swapped

U900

and

U700 again to no avail. Will continue searching for sweeps that might

work and

looking at that opamp.

On Mar 21, 2019, at 12:50 AM, Reed Dickinson <reed714@...> wrote:

Hi Ripley:

You are correct, do not connect to the focus lead, a blob of silicon seal should work. You need to splice the cable going from the tripler to the socket. Slide a piece of shrink wrap tubing over a piece of thick wall plastic tubing over the wires to be spliced, make sure that you have a good lapping solder joint. After the joint cools look closely and be sure there are no sharp pieces of wire showing then generously coat the entire joint with silicon sealer and slide the large piece of tubing over the joint then slide the shrink tubing over the plastic tubing and heat the shrink tubing to seal it. If it is loose use two small tie wraps. Mount the mew tripler where the old tripler was by drilling two holes and install screws. Next connect the transformer output to the IN terminal using a .01uF, 5KV or 10KV cap. The cap must be used to make it work. Connect up and fire it up. Good luck!


Reed

On 3/17/2019 5:28 PM, SuddenLink wrote:
Hi Reed,

I received the NTE539 a few days ago and pulled out the existing HV trippler these evening. It is going to be a tight fit but it looks I can squeeze the new trippler in it’s place. The question is, what do I do with the Focus tab on the NTE539. I am thinking that it gets clipped off and covered with a glob of silicon seal.

I am going to hold off until I hear back from you.

Thank you.

Ripley

Sent from Mail for Windows 10

From: Reed Dickinson
Sent: Tuesday, March 5, 2019 3:11 PM
To: [email protected]
Subject: Re: [TekScopes] 475 with no Display and no HV

Hi:
See answers in red below.

Was this the 2465B that had the CTS installed? If so, pull all the
plugs, and install jumpers on J102, pins 3&4, 1&7, and J101 pins 1&3, 6&8.

The sweep won't work if those paths aren't connected... for whatever reason.

-Chuck Harris

Siggi wrote:

I’d look at the A5 timing reference signals next. Those go to DR of U700
and get compared with the ramp voltage to gate the B sweep. On the A5 board
they’re DLY REF 0/1.

NB: did you try dual delay sweeps? I believe that mode will use only the A
sweep, but alternate the delay between the two control voltages, allowing
you to see whether the controls are responsive.

On Tue, Mar 19, 2019 at 19:56 <thespin@...> wrote:

1. No sweeps seem to work
2. The opamp outputs look close enough that I'm inclined to assume they're
doing their job
3. THO on U900 appears stuck high for all front panel configurations I
could test. It dips low momentarily when turning the sec/div knob, but
shows no periodic behavior.

On Tue, Mar 19, 2019 at 07:20 PM, <thespin@...> wrote:

I've tried cleaning U500 and U900 to no avail, and then I swapped U900

and

U700 again to no avail. Will continue searching for sweeps that might

work and

looking at that opamp.

Hi Reed,

I received the NTE539 a few days ago and pulled out the existing HV trippler these evening. It is going to be a tight fit but it looks I can squeeze the new trippler in it’s place. The question is, what do I do with the Focus tab on the NTE539. I am thinking that it gets clipped off and covered with a glob of silicon seal.

I am going to hold off until I hear back from you.

Thank you.

Ripley

Sent from Mail for Windows 10

From: Reed Dickinson
Sent: Tuesday, March 5, 2019 3:11 PM
To: [email protected]
Subject: Re: [TekScopes] 475 with no Display and no HV

Hi:
See answers in red below.
On Tuesday, March 5, 2019, 11:55:54 AM PST, Jim Olson <v_12eng@...> wrote:
I'm curious where the Museum is located it sounds interesting to me too I'm in the SF bay area.

Jim O

On March 5, 2019 at 4:55 AM SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:


? ? Hi Reed,

? ? Yes sir working at the Radio Museum is a lot of fun and hard work at the same time but now that I am retired it is a great place to volunteer a few days a week.

? ? Between the NTE539 and NTE538 which one would you recommend for the Tektronix 475?

The NTE539 is the most suitable but if you get a 538 you need to connect the D lead to the LOW wire and connect both to ground.? Using the 539 connect LOW to ground, leave the FOCUS terminal open and connect the cap from the transformer to the IN terminal,? Either the 538 or the 539 MUST have a ,01uF, 5KV or 10KV cap between the transformer and the IN terminal.? NOt installing the cap will fry the multiplier in seconds.
Reed

? ? Ripley

? ? The words are mine but this iPad does what it will with them.

? ? ? ? > > On Mar 5, 2019, at 12:08 AM, Reed Dickinson <reed714@... mailto:reed714@... > wrote:

? ? ? ? Hi Ripley:
? ? ? ? Wiring in a NTE538 is a little different than wiring in an NTE539. When you get your 3Xer write ma back and I will detail how to do it.
? ? ? ? Your antique radio setup sounds most interesting. I would probably be helping you out at that facility if it were on the left coast.
? ? ? ? Reed
? ? ? ? On Monday, March 4, 2019, 4:43:02 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:

? ? ? ? Hello Reed,

? ? ? ? You just have been reading my mind. I was wondering how to handle the HV lead out to the CRT. What about the Focus Tap on the module. I am guessing that is left unterminated and highly insulated from anything around it.

? ? ? ? Our plan is to repair the scope so that we can sell it. The Museum of Radio and Technology is a nonprofit all volunteer organization. We don’t charge for admission so our revenue sources are from cash donations, sales from our gift shop , small grants, and the three swap meet/auctions that we host every year.

? ? ? ? Museum of Radio and Technology

? ? ? ? I will keep everyone posted as I bring this repair to completion.

? ? ? ? Ripley

? ? ? ? Sent from Mail for Windows 10

? ? ? ? From: Reed Dickinson
? ? ? ? Sent: Monday, March 4, 2019 4:59 PM
? ? ? ? To: [email protected] mailto:[email protected]
? ? ? ? Subject: Re: [TekScopes] 475 with no Display and no HV

? ? ? ? Hi Ripley:
? ? ? ? Good show, a new 3X voltage multiplier will get your 475 back on the air. If you elect to get an ECG or NTS 538 or 539 you will have to splice the HV lead leaving the new tripler. I very carefully slip a piece of thick wall plastic tubing over where the splice will be, carefully solder the joint leaving NO sharp points, coat the entire joint with silicone and slip the tubing over the joint. I put a small tie wrap over each end to keep moisture out. The 538 or 539 will fit in the space the present tripler is in, you will need to drill two mounting holes for the retainer screws.
? ? ? ? Reed Dickinson
? ? ? ? On Monday, March 4, 2019, 1:40:15 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:

? ? ? ? Hi Reed,

? ? ? ? Per your suggestion I disconnected the wire from the secondary of T1320 to the voltage tripler and powered up the scope. The waveform at TP1318 immediately snapped to 32 volts p-p at about 70Khz without any persuasion via the 1K resistor trick. I also checked the oscillator over at the junction of CR1329 an C1326. It measures 320 volts p-p so it looks like I need to order a voltage tripler module.

? ? ? ? Thank you so much for your help. Obviously, you know your way around these scopes.

? ? ? ? Ripley

? ? ? ? Sent from Mail for Windows 10

? ? ? ? From: SuddenLink
? ? ? ? Sent: Sunday, March 3, 2019 8:27 PM
? ? ? ? To: [email protected] mailto:[email protected]
? ? ? ? Subject: Re: [TekScopes] 475 with no Display and no HV

? ? ? ? Hello Again,

? ? ? ? I went back to the circuit around Q1306 and Q1308 this evening. The resistors are all within specs. C1305 was pulled and checked. It is also fine. C1304 is good and so is C1302.
? ? ? ? By the way I am checking the capacitors with a DE-5000 LCR meter. It was never let me down yet.

? ? ? ? The only component that I have not replaced or substituted is Q1306. It checks fine on my little Chinse component tester. For whatever that is worth.

? ? ? ? Enough for today.

? ? ? ? Ripley

? ? ? ? Sent from Mail for Windows 10

? ? ? ? From: Steph L
? ? ? ? Sent: Sunday, March 3, 2019 7:05 PM
? ? ? ? To: [email protected] mailto:[email protected]
? ? ? ? Subject: Re: [TekScopes] 475 with no Display and no HV

? ? ? ? Hi Ripley,
? ? ? ? How about C1305 0.1uF.
? ? ? ? If open, gain of Q1306 (and whole oscillator loop) will be lower and perhaps not enough to maintain oscillation? (Great suggestion from Don re 1K pull up touch on Q1318 base.)
? ? ? ? Steph

? ? ? ? PS. Still nubie here and unsure which "Reply" button to click on. I clicked on Ripley's "what the heck?" message "reply" button and see it has been inserted a few messages prior! That is really confusing. I'm in Melbourne Oz GMT +10 hrs. Is this the reason (i mean time difference guys and not quirky)


















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Museum of Radio and Technology

The Museum of Radio and Technology is one of the largest antique radio museums in the United States. See vintage...
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Re: 475 with no Display and no HV


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