Tek 475 scope

[hevans1944]

Wow, what a patronizing load of crap.

Really? I am sorry you feel that way as I have seen @dorke give some very helpful advice to newbies on other threads. Quoting from your first post:

Just bought this scope on ebay ... Never been in a scope before. I got interested in electronics a couple of years ago ...all the while trying to learn something. Got a looong way to go. I was considering removing transformer to check it but really hate to tear things apart unless I am pretty sure of what I am doing. So I thought maybe someone with experience on scopes might give me some suggestions.

You got your "someone with experience on scopes" who started to give you some step-by-step suggestions, but it is clear from your response you don't feel you needed his help with this. So, go ahead and whip out your Weller soldering gun and remove that transformer. @dorke merely suggested an alternative troubleshooting path, appropriate for a "newbie" with two years of experience who until now had never seen the inside of a commercial oscilloscope. Do whatever you want. Maybe even follow @73's de Edd 's advice, which was similar to @dorke. Edd has been around the block a few times, and is generally well-informed, as are several members of EP.

 

[dorke]

Well Corri,
As the saying goes :"You can't teach an old dog new tricks ",it goes without saying, nor any wisdom either.
Best of luck.I'm out of here.

 

[(*steve*)]

One of these days, when the trauma is a little less, I may tell you a story about what happens when you dive in to repairs too quickly.

 

[Corri]

dorke, I don't know if you will read this but I just want to apologize for my response to your post. I was out of line and am sorry for it. I could tell you what lit my fuse but I was wrong and will not make excuses. Best of luck in your life.

 

[Corri]

Sir Corri . . . . .

After initially finding that you are Amerikanski . . . .and will be using 120VAC power. . .along whth that ohms reading across the primary of the power transformer . . . .is looking as normal.
MY next step would be to switch DVM to AC metering mode and measure the line voltage to initially confirm that you DO have a good working AC mode DVM.
Then you move over to the secondary of the transformer for those 4 windings shown there on post #10 and check for the lowered AC voltage presence there on all of them, and then, if all being present, move to the raw DC filters that they feed and confirm DC presence.

All are marked up and board placements are being shown. You just need to confirm against PCB stampings.

If having all voltages present . . .the reg supplies follow.

Thassssssit . . . .
Currently in my test equipment stable . . . of just this series . . . (2) - 465's (1) - 466 Storage scope
(1) - 475 . . . .WITH the DVM pack on its top.


A9 CARD PARTS PLACEMENT REFERENCING . . . . .

View attachment 41338

73's de Edd
.....

Scope back together and this is what I have. AC supply at 122.4 v. c1462-3.446v, c1452-13.22, c1472-13.02, cr1462-3..44v. I don't know how to get readings on the other cr's. Cr1462 is mounted high enough to probe it but the rest are mounted flat to board. Is there a way to check them that I didn't see?

 

[(*steve*)]

With the aid of the circuit diagram and/or the PCB layout you should be able to locate other components connected to the leads of the capacitors you can't access.

 

[73's de Edd]

Sir Corri . . . . .

After initially looking at those readings . . . . the DVM is properly coming up with the AC line voltage.
The other readings look as if you are using a ground and reading to the FWB rectifier blocks.
Consulting the . . . . HIGHLY DEFINED fotie-graf-a-mus-us . . . . pick the side view of the -8V Full
Wave Bridge rectifier and the defined point to take the AC readings from would be the two center leads
that have the AC sine symbol.

That one is easy to get to, I usually use multiple flying leads for hard to get to points, temporarily solder
tacked on and then routed out and tagged to be able to take the readings from the ends . . . "outdoors".

SINCE you do reveal static AC readings, ye olde transformer is a transforming.
So, now just go to DC mode in metering and pick out the BLACK ground reference for your meters
negative lead, for all of these voltages to be metered and the other voltage test points are all clustered around it .

The one exception is being the -15 which is far to the left and just to the right of its CR1472 rectifier block.

See what Dee Cee voltage readings you get now.

POWER SUPPLY PARTS CLOSEUP OF THEIR LAYOUT . . . . . . .

H-Dee
(Takes a minute or so . . . .or if you use 2 short rings and one long ring
on your party line phone . . .or our neighbor, Junior . . . even with his new
fangled BR-549 number, it even takes him a while. )

Left clickee-clickee . . . . it makee mo' biggah

https://image.ibb.co/n3S8k8/TEK_575_Pwr_Supply.png

Or fax quality . . .

https://ibb.co/cQkuQ8

73's de Edd
.....

 

[Corri]

Sir Corri . . . . .

After initially looking at those readings . . . . the DVM is properly coming up with the AC line voltage.
The other readings look as if you are using a ground and reading to the FWB rectifier blocks.
Consulting the . . . . HIGHLY DEFINED fotie-graf-a-mus-us . . . . pick the side view of the -8V Full
Wave Bridge rectifier and the defined point to take the AC readings from would be the two center leads
that have the AC sine symbol.

That one is easy to get to, I usually use multiple flying leads for hard to get to points, temporarily solder
tacked on and then routed out and tagged to be able to take the readings from the ends . . . "outdoors".

SINCE you do reveal static AC readings, ye olde transformer is a transforming.
So, now just go to DC mode in metering and pick out the BLACK ground reference for your meters
negative lead, for all of these voltages to be metered and the other voltage test points are all clustered around it .

The one exception is being the -15 which is far to the left and just to the right of its CR1472 rectifier block.

See what Dee Cee voltage readings you get now.

POWER SUPPLY PARTS CLOSEUP OF THEIR LAYOUT . . . . . . .

H-Dee
(Takes a minute or so . . . .or if you use 2 short rings and one long ring
on your party line phone . . .or our neighbor, Junior . . . even with his new
fangled BR-549 number, it even takes him a while. )

Left clickee-clickee . . . . it makee mo' biggah

https://image.ibb.co/n3S8k8/TEK_575_Pwr_Supply.png

Or fax quality . . .

https://ibb.co/cQkuQ8

73's de Edd
.....

OK, you will probably give up on me but this is what I have.On the caps, using meter on dc. c72-25.19, c62-13.77, c52-12.93, c12,14,42-0. On ac, meter goes to .025 0n c72,62, 52, 12, 14, 42. Same with cr62, center legs .025. With meter on dc, using ground as shown the meter instantly goes to .oooo on all test posts. I didn't follow through on rest of rectifiers because of these readings and because even with your instructions I still cannot see where you are finding test legs. Where you have the red circle this board has a diode, resistor and polarized cap that also reads .025 on ac. If you are beginning to think I have a box of parts here I sure couldn't blame you. I know being from Texas you are smart. I spent a year in Texas many,MANY moons ago and I got smarter. One night in the San Antonio drunk tank smartened this old farm boy right up. Anyhow, I await your answer with bated breath.

 

[73's de Edd]

Sir Corri . . . . .

On the caps, using meter on dc.
c72-25.19, c62-13.77, c52-12.93, c12,14,42-0.
On ac, meter goes to .025 0n c72,62, 52, 12, 14, 42. Same with cr62, center legs .025.
With meter on dc, using ground as shown the meter instantly goes to .oooo on all test posts.
I didn't follow through on rest of rectifiers because of these readings and because even with your instructions

If you were reading the electrolytic capacitors that are associated and being fed by its like numbered bridge rectifiers.It seems that you just spaced between them with a dash, and a following comma in your given series of voltage readings.

That should have C72 being designated as a negative / minus voltage reading, as is C62's readings.
One should expect negative DC voltages on C72 and C62 caps, with POSITIVE DC voltages on associated caps C52-12 . . .AND your unremitted +15 voltage, which was not given, which is being a major supply voltage on that unit.

I still cannot see where you are finding test legs.
I was carefull to place my BLACK with RED numbering for POSITIVE voltages or BLACK with WHITE lettering for NEGATIVE voltages, right beside the test lugs. yet I didn't want to block the view.

Lets look at the BLACK GND label with its WHITE lettering inside.

The test stake / point is a lug that raises vertically and separates enough to make an oval opening and then close again at the top . . .there is an oval hole thereby being made within that eyelet stake type of terminal .. The +15 is just to the right of its BLACK label, as are all of the others, being spread around the immediate area.
My RED circle merely is a pre marking of a common problem area, which will have to be seen if it is relevant to your situation, later on .
THE given DC voltages that you submitted was sort of in order, excepting for the additional polarity identifications being needed.
The submitted AC voltages in mere millivolts, were signifying a good level of filtering action with no developed ripple due to overcurrent consumption of that voltages circuitry OR a time related decline of capacitance value of that particular filter.

Trying again, with the meter in DC mode and its black lead using that BLACK ground test stake, the other RED meter test lead should easily reach the nearby +15 - - - - -+5 - - - - - -Minus 8 - - - -+5 - - - -+50 - - - - -+110 and then a far stretch over to the -15 stake , just to the right of its -15 Rectifier diode package .

Thassssssssit . . . . .

73's de Edd
.....

 

[Corri]

Sir Corri . . . . .

On the caps, using meter on dc.
c72-25.19, c62-13.77, c52-12.93, c12,14,42-0.
On ac, meter goes to .025 0n c72,62, 52, 12, 14, 42. Same with cr62, center legs .025.
With meter on dc, using ground as shown the meter instantly goes to .oooo on all test posts.
I didn't follow through on rest of rectifiers because of these readings and because even with your instructions

If you were reading the electrolytic capacitors that are associated and being fed by its like numbered bridge rectifiers.It seems that you just spaced between them with a dash, and a following comma in your given series of voltage readings.

That should have C72 being designated as a negative / minus voltage reading, as is C62's readings.
One should expect negative DC voltages on C72 and C62 caps, with POSITIVE DC voltages on associated caps C52-12 . . .AND your unremitted +15 voltage, which was not given, which is being a major supply voltage on that unit.

I still cannot see where you are finding test legs.
I was carefull to place my BLACK with RED numbering for POSITIVE voltages or BLACK with WHITE lettering for NEGATIVE voltages, right beside the test lugs. yet I didn't want to block the view.

Lets look at the BLACK GND label with its WHITE lettering inside.

The test stake / point is a lug that raises vertically and separates enough to make an oval opening and then close again at the top . . .there is an oval hole thereby being made within that eyelet stake type of terminal .. The +15 is just to the right of its BLACK label, as are all of the others, being spread around the immediate area.
My RED circle merely is a pre marking of a common problem area, which will have to be seen if it is relevant to your situation, later on .
THE given DC voltages that you submitted was sort of in order, excepting for the additional polarity identifications being needed.
The submitted AC voltages in mere millivolts, were signifying a good level of filtering action with no developed ripple due to overcurrent consumption of that voltages circuitry OR a time related decline of capacitance value of that particular filter.

Trying again, with the meter in DC mode and its black lead using that BLACK ground test stake, the other RED meter test lead should easily reach the nearby +15 - - - - -+5 - - - - - -Minus 8 - - - -+5 - - - -+50 - - - - -+110 and then a far stretch over to the -15 stake , just to the right of its -15 Rectifier diode package .

Thassssssssit . . . . .

73's de Edd
.....

73's de Edd
I will try to make myself more clear. Starting with meter on DC. Test points as you clearly described, starting with gnd. and continuing in clockwise rotation it is +15/+.0000, -8/meter shows only.0000, +110/-.010, +50/+.0000, -15/+.0000. To be more clear on minus/8 and minus/15 the meter does not show minus regardless of switching probes. When I said I could not find test points you referred to, such as the ones you said you soldered flyers on, what I meant was the test points for the rectifiers such as cr62 which read .025. Sorry I wasn't more clear. My fluke meter reads, as I am sure you are aware of, + readings with no designation as to + or - unless it is minus and then reads -. Continuing on to C72 cap and c62 cap if I reverse meter leads I get minus readings on both. I had assumed that plus pin was always in center between the two supporting pins on the caps. Guess that was wrong also. Hope this helps.