SAE Mark Six issues

[Descartridge]

Acquired one of the "coolest looking tuners". please see below.
It does work.
However it has a few significant issues:

1. The dial will not not move from 102.7, and
2. the graphic display will not illuminate.

It has been cleaned and brought up on a variac.

Does anyone have any experience with this item?
Or know where I can get a service manual or schematic?

Thanks.

 

[sregor]

Someone should be along who knows more than I. What I do know, is that the tuner is an analog tuner, and the digit display runs off the local oscillator through a buffer and a prescaler. The tuning system is a regular ganged capacitor type - don't recall if it is run by a dial string or directly off the tuning knob. Does it change station - if not look for a mechanical problem. Cool tuner.

 

[Descartridge]

Someone should be along who knows more than I. What I do know, is that the tuner is an analog tuner, and the digit display runs off the local oscillator through a buffer and a prescaler. The tuning system is a regular ganged capacitor type - don't recall if it is run by a dial string or directly off the tuning knob. Does it change station - if not look for a mechanical problem. Cool tuner.

Thanks S,
The station indicator only changes from 102.7 to 102.5.

 

[Punker X]

Worked on quite a few of these. I got blue print size scats prints from the SAE collector who's gear I was working on.

Is your belt ok? Meaning when you turn the tuning knob it's turning the front-end? Check the connection from the local osc to the display board. Check the low voltage display board.

Being stuck like it is sort of tells me the front end is probably not moving. Other issues typically either give you no display or wildly changing or the display running up or down.

Very nice and unique tuners when working properly. I'd love to own one one these days.

 

[Punker X]

I see also that the oscope is not working. Typcially bad caps in the high voltage power supply, seen bad diodes and caps cause these issues. Rarer and much more expensive to repair... a bad transformer or CRT.

 

[MilEastSider]

Sae mk vi

I once had one of these SAE tuners which I regret selling. It was a slightly newer model with push buttons instead of paddle switches. But I think the electronics were similar.

I had a flickering digital readout problem - different then your symptom.

As I recall, the problem was due to a cold solder joint in one of the boards. I found the problem (I think by slightly tapping or wiggling the board) and fixed it.

All I'm saying is the problem might be something really simple like this. As I remember, the tuner was built like a tank. Everything was really high quality.

After fixing my tuner, I then put it in the newspaper classifieds (around 1988 - pre internet days). A guy saw the ad, called me in a desperate sounding voice "Do you still have the tuner?" and came by almost immediately. If memory serves me correctly, we exchanged $250 at the front door and he was gone in a flash along with the tuner. I felt like I had just done a drug deal.

I went though so many old pieces of gear in those days. I'd fix them and re-sell them, like a used car dealer does with cars. But I wish I had hung onto this one.

 

[MilEastSider]

Additional Info

I forgot to mention in my last post.

Go to:

www.jims-sae-site.com

This site has a lot of detailed SAE information. As I recall, he will supply manuals for a small fee.

Mike

 

[Descartridge]

Thanks Mike.
I will try tapping the joints and boards and then contact Jim.

Many thanks to Punker, I do have the stations moving, with a new belt (a square one not the stretched round original one).
All of the caps seem to test good.
I just need the scope to work. I may be looking at an "investment".
I cannot believe the value of one on the auction site in the same condition as mine.
Thanks again.

 

[chicks]

That looks cooler than my MK-VIII / 8000. Love the Nixie tubes vs. the LED's.

Same broken belts issue, found exact replacement o-rings at Ace hardware.

 

[Descartridge]

Thanks for the tip, Chicks!

 

[onemug]

RDecartridge,

Don't know if you have tried this but for your scope issue, have you played with the 4 black knobs to the right of it? I have a Mark VI. It's possible to reduce the intensity to where it disappears completely and you can move the display off the screen with the H/V knobs.

Start with turning the intensity knob all the way up (clockwise as I remember), then rotate the horizontal and vertical knobs both ways and see if you can "find" the display. If this works, center the display and reduce the intensity to the lowest brightness you like. Hope you get lucky.

 

[Punker X]

Good points..

Been been my experience most of the time it's high voltage cap problems with tuner oscope issues.

Pretty sure the MK6 had transformer issues and had a service note, the issue was addressed with the MK6B.

 

[Descartridge]

RDecartridge,

Don't know if you have tried this but for your scope issue, have you played with the 4 black knobs to the right of it? I have a Mark VI. It's possible to reduce the intensity to where it disappears completely and you can move the display off the screen with the H/V knobs.

Start with turning the intensity knob all the way up (clockwise as I remember), then rotate the horizontal and vertical knobs both ways and see if you can "find" the display. If this works, center the display and reduce the intensity to the lowest brightness you like. Hope you get lucky.

Thanks Mug,
I will try it. But, the shaft of the intensity pot is broken off and i will try some needle nose pliers to move it.
Is there anything special; about this pot? that I need to know before I replace it?

 

[onemug]

Thanks Mug,
I will try it. But, the shaft of the intensity pot is broken off and i will try some needle nose pliers to move it.
Is there anything special; about this pot? that I need to know before I replace it?

Bummer on the shaft. I know nothing about the pot, I'm sure Mike will have some suggestions. Good luck with the pliers.

 

[Negotiableterms]

On my Mk VIB, the scope changes displays from lissajous to tuning when the tuning knob is touched. IIRC, the VI worked the same way. Could that mechanism cause the trouble?

 

[Punker X]

Thanks Mug,
I will try it. But, the shaft of the intensity pot is broken off and i will try some needle nose pliers to move it.
Is there anything special; about this pot? that I need to know before I replace it?

Does this unit have the plastic shafts? I'd have to dig out the scats to make sure, but pretty sure there is high voltage going thought those pots, thats the reason they have plastic shafts. Don't dig in there with needle nose with the power on. Another unobtainium part.

 

[Descartridge]

Does this unit have the plastic shafts? I'd have to dig out the scats to make sure, but pretty sure there is high voltage going thought those pots, thats the reason they have plastic shafts. Don't dig in there with needle nose with the power on. Another unobtainium part.

thanks Mike
Yes, it is a pot with a plastic shaft.
I was able to turn it with a plastic rod- still no display.:tears:

 

[mr bob]

Hifi Engine has the schematic for the scope section on the MK VI, in case you need it. And for the tuner section. Not the display section. Anybody know where I can get a schematic for the Nixie tubes display? And the tubes? They are all dim and not changing a whit even tho the owner says the tuner is picking up stations just fine. They need to be replaced, but that won't bring back ops, it will be the circuitry in front of them that will. Need to get both done. Scope works fine as well, as is.

 

[AdamAnt316]

Hifi Engine has the schematic for the scope section on the MK VI, in case you need it. And for the tuner section. Not the display section. Anybody know where I can get a schematic for the Nixie tubes display? And the tubes? They are all dim and not changing a whit even tho the owner says the tuner is picking up stations just fine. They need to be replaced, but that won't bring back ops, it will be the circuitry in front of them that will. Need to get both done. Scope works fine as well, as is.

This is an old thread, so not sure if the OP is still around. If all the nixie tubes are evenly dim, I'd probably look towards the power supply feeding them before pointing fingers at the tubes themselves. Nixie tubes generally need somewhere around 170 volts DC to light them, so (carefully!) check the output of their HV power supply to see if the tubes are getting their voltage. If they aren't, bad capacitors would be the likely culprit; try changing any electrolytic capacitors in the nixie supply. As for why the display isn't changing, check the belt(s) as mentioned above. Good luck!
-Adam

 

[atmer]

mr bob,

The only schematic of the nixie board I'm aware of is a hand drawn schematic by technician Mike Zuccaro, I don't think SAE ever released one.
That being said, I would try changing the dual gate mosfet mixer, 40673,40823(SAE could have used either) located on the rf board attached to the front end as that feeds the nixie board or the first IC, SN74S112N located on the nixie board itself to see if that gets the counter running. The nixie tubes will have to be changed as there is a silver coating that collects on the inside of the tube after very extended use.

Hope that helps,
John