Anyone near Rotherham who could test my Scope?

ericgibbs · Aug 22, 2008

hi Al,
Sorry about the delay.

Been doing a bit of outdoor house painting.

Tidied up the drawings for the scope this morning.

Will add your voltages to the dwg and post a few suggestions.

1*transistor*1 · Aug 22, 2008

hi,

i used to have a scopex oscilloscope but one day i switched it on and the crt exploded!!
so i wouldnt be surprised if it fails but good luck: hope it works.

ericgibbs · Aug 22, 2008

1*transistor*1 said:
hi,

i used to have a scopex oscilloscope but one day i switched it on and the crt exploded!!
so i wouldnt be surprised if it fails but good luck: hope it works.

hi,
Serious question.

Did you dump it or strip out any spares.?

Im sure Al would be interested.

1*transistor*1 · Aug 22, 2008

bigal_scorpio said:
Here'e my scope service manual, or for anyone with a Scopex 14d-10(v)

i used to have a scopex oscilloscope but one day i switched it on and the crt exploded!!
so i wouldnt be surprised if it fails but good luck: hope it works.

1*transistor*1 · Aug 22, 2008

bigal_scorpio said:
Hi to all,

Thanks for all the info past, present and future guys. You have got me through some difficult problems!

After following a link from kchriste about Oscilloscopes I am beginning to think mine may be faulty. Its an old one that I acquired and never had instructions or specs for.

To be honest I cant even follow basic "How To" guides as my scope and the tutors never seem to have the same controls or parts!

E.G. in one guide it mentions the probe test that gives a square wave output, I have a test probe point but I cannot get a square wave from it, just a constant 4v trace!

Also I have never managed to get anything from the "A probe" and can even only get a test signal on "B" but I do get wild traces when touching the probes with fingers.

What I need is someone with scope expertise to check mine and maybe just get me going with what means what with my seemingly unusual scope (Scopex 140-10V). I would be quite happy to travel a reasonable distance if anyone is willing to help and show me the ropes or condemn my scope!

I live in Rotherham, close to the Meadowhall shopping center and M1.

If anyone can help please let me know. I am sure Eric Gibbs would help me as he has done with advice many times in the past but sadly he lives hundreds of miles away from me, maybe I should consider flitting closer hehehe, but seriously any help will be greatly appreciated.

Thanks for reading my plea................Al[/hi,

i used to have a scopex oscilloscope but one day i switched it on and the crt exploded!!
so i wouldnt be surprised if it fails but good luck: hope it works.]

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi Eric,

Results as follows:-

1 = -1v3
2 = +5v6
3 = +15v1
4 = +15v1
5 = +15v1
6 = +180v
7 = +180v
8 = +14v4 measured on collector
9 = +14v4 measured on collector
10 = -15v1 one end 0v other end
10a = 15v1 both ends

I am not an expert by any means, but I have noticed that one of the +15v1 seems to be -15v1 on the drawing is this an error or a fault on board?

Hoping these will help solve my problem...........Al

hi Al.
The M151 [733] looks right out of balance.

If you measure on M251 pins 7 and 8 they should both be about the same voltage.

From the ends of the R148 and R149 [150R] reistors are a Yellow and Green wires.
Remove these two wires from the pins [make sure they cant touch anywhere]

The two pins where the wires came off, connect together and ground to 0V.

This will make the inputs to the M151 amp at the same potential and the voltages on pins 7 and 8 should be the same.

Its all pointing towards a duff TR152 [fet].

Look at my attached dwgs and add the NEW voltages measured at pins 7 and 8.

Lets know what you find.

bigal_scorpio · Aug 22, 2008

Hi Eric,

On the drawing you just posted the TR152 and TR153 seem to be duplicated lower down, well I nthink it says TR153 its a bit blurred, but there are definately 2 TR152s shown on the drawing!

This is baffling me as there is only one FET granted its a dual one but the drawing shows 4 connections to what I can only assume is 1 dual FET, how does this work? Is mine missing a dual fet?

Is it worth me listing my FETs to see if any will do as subs?

Al

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi Eric,

On the drawing you just posted the TR152 and TR153 seem to be duplicated lower down, well I nthink it says TR153 its a bit blurred, but there are definately 2 TR152s shown on the drawing!

This is baffling me as there is only one FET granted its a dual one but the drawing shows 4 connections to what I can only assume is 1 dual FET, how does this work? Is mine missing a dual fet?

Is it worth me listing my FETs to see if any will do as subs?

Al

hi,
I'll have a closer look at the photo's.

Have you had chance to remove the pair of wires from the 'top' 733 [M151] and ground the two pins to 0V.
Just do it for the top amp at the moment.

bigal_scorpio · Aug 22, 2008

ericgibbs said:
hi,
I'll have a closer look at the photo's.

Have you had chance to remove the pair of wires from the 'top' 733 [M151] and ground the two pins to 0V.
Just do it for the top amp at the moment.

Hi eric,

Was just about to do it, do you mean the top 2 wires in the photo you sent?

Al

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi eric,

Was just about to do it, do you mean the top 2 wires in the photo you sent?

Al

hi,
The top amp in the schematic M151.
Its the bottom pair in the photo.

The FET area is not the same as the dwg.
The component values are also different to the schematic.

Is there any writing on the EL421 case.?

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi Eric,

On the drawing you just posted the TR152 and TR153 seem to be duplicated lower down, well I nthink it says TR153 its a bit blurred, but there are definately 2 TR152s shown on the drawing!
Al

hi,
Its most likely me misreading the blurred dwg.

Iv'e rechecked the U421 pdf, which I understand is the metal case equivalent of the E421, its got 6 wires for sure.

bigal_scorpio · Aug 22, 2008

ericgibbs said:
hi,
Its most likely me misreading the blurred dwg.

Iv'e rechecked the U421 pdf, which I understand is the metal case equivalent of the E421, its got 6 wires for sure.

Hi Eric, mine says U441 on it and this comes up as a dual Fet, heres the sheet

Maybe they are more easily obtainable or possibly I may have a couple of single Fets that I could use, this would be best as I could do it now!

Regards................Al

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi Eric, mine says U441 on it and this comes up as a dual Fet, heres the sheet

Maybe they are more easily obtainable or possibly I may have a couple of single Fets that I could use, this would be best as I could do it now!

Regards................Al

hi,
I'll look thru it.

The test you doing at the moment, with the wires off, will tell us if the M151 [733] is OK.

Once we have established that, we will move on to the source follower FET.

My aim is to get at least one channel fully working with sync, so that you can use the scope. Then we can look at the other channel.OK.

bigal_scorpio · Aug 22, 2008

ericgibbs said:
hi,
I'll look thru it.

The test you doing at the moment, with the wires off, will tell us if the M151 [733] is OK.

Once we have established that, we will move on to the source follower FET.

My aim is to get at least one channel fully working with sync, so that you can use the scope. Then we can look at the other channel.OK.

Hi Eric,

The 733 now measures -1v5 on pin 7 and +6v4 on pin 8. Wires off and pins grounded.

Does this tell you something?

Al

ericgibbs · Aug 22, 2008

bigal_scorpio said:
Hi Eric,

The 733 now measures -1v5 on pin 7 and +6v4 on pin 8. Wires off and pins grounded.

Does this tell you something?

Al

hi Al,
Its suggesting the 733 is faulty/

You could swop the two 733's over, dont get them mixed up.

Then see what you get on pin 7 and 8

EDIT:
This image shows how it should be connected on the inputs.

Farnell will get the U441, expensive.!!!!!

ericgibbs · Aug 22, 2008

hi Al,
This link is showing U441 in stock.

Deleted the link... it was showing my email address!

bigal_scorpio · Aug 22, 2008

Hi Eric,

Looks like I will be tryig to find a 733 now then aswell!

As for the U441, couldn't I pair of single fets, I have some, I will send you the sheets to the four I think most suitable if you would be so good as to have a look at the specs.

I hope we can use some of them as it would mean not just saving cash, but more importantly that I could do it sooner!

BTW 2N5047 is given as a substitute for the E421 (441) in one of my ancient equivalent books, it says dual fet - I believe the 2N5457 is the single equiv!

Al

ericgibbs · Aug 22, 2008

Looks like I will be tryig to find a 733 now then aswell!

Hi Al,

Did the swop over test indicate a faulty LM733.????

Downloaded your pdf's. Let you know.

EDIT:
Its your lucky day.!
I have 4, NE592 equivalents to LM733 on the shelf, If required I can send you 2 by post. [free]

Lets know.

I do have some LM733 metal can style somewhere, but it would mean mounting on a header.

EDIT2:

All your FET's are Audio range or switching...
The best match I can see at the moment, from the web, is the PMBF J620.

You are going to have to buy the U441's...

EDIT3: added a simplified dwg of one Y amp, it should help with testing.

bigal_scorpio · Aug 23, 2008

Good morning Eric,

I do think I have a faulty 733!

The 733 now measures -1v5 on pin 7 and +6v4 on pin 8. Wires off and pins grounded whichever socket its in!

So I would be grateful to take you up on your kind offer mate.

Putting them on headers would be no problem, not after making the adaptors for the CAs anyway See attachment, not pretty but functional!

I have been trying to find other sources for the U441 while I was doing nothing and found one on ebay, have a look, is that for 1?

**broken link removed**

And whats with the postage, he is in England, not the USA!

Makes the link you sent me look cheap mate, think I will send for one from there.

Anyway thanks again Eric and fingers crossed I will eventually get a working scope

Regards..............Al

ericgibbs · Aug 23, 2008

bigal_scorpio said:
Good morning Eric,

I do think I have a faulty 733!

The 733 now measures -1v5 on pin 7 and +6v4 on pin 8. Wires off and pins grounded whichever socket its in!
I assume the 'other' LM733 gives the correct output voltage.???

Putting them on headers would be no problem, not after making the adaptors for the CAs anyway See attachment, not pretty but functional!

The NE592 is a DIP direct replacement, no header required.
I'll post them Monday 25th. OK.

I have been trying to find other sources for the U441 while I was doing nothing and found one on ebay, have a look, is that for 1?
Thats expensive for one!.
If you plan to use the scope for some years, I would buy at least 3 from the web.

**broken link removed**

And whats with the postage, he is in England, not the USA!

Makes the link you sent me look cheap mate, think I will send for one from there.

Anyway thanks again Eric and fingers crossed I will eventually get a working scope

Regards..............Al

Hi,
Look at the last dwg I posted, it should help as a guide.

Anyone near Rotherham who could test my Scope?

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