The Combine Forum banner

21 - 32 of 32 Posts

·
Registered
Joined
·
6 Posts
That's good to know about the issues with digital... I was awfully tempted to go that route if I couldn't find a solution my self.. but this makes me want to keep it as original as possible... after all the thing is older than me and worked so good, for so long...

Besides the digital issues mentioned I really didnt want to send it away because it has the original old ound needle meter on the front, I think they just look so cool, and I hate the looks of the new plastic square ones.

I suppose checking the vacuum tubes is the next logical step, i read online they should be warm... neither one is on mine but when removed, the needle fails to move at all, so they are doing something...
They don't rattle and are not discolored.

What's the chance someone would have a wiring schematic for a 919 with vacuum tubes?
The schematic can be found in older Book of Charts. 1980 perhaps. I can supply one if you like
 

·
Registered
Joined
·
39 Posts
I have one seems to be very inconsistent. When the moistures high the sample is drier than it says when comparing to elevator. And when it’s dry the sample is wetter than it says. What could that be? Thanks
 

·
Registered
Joined
·
6 Posts
It sounds like the calibration in the middle is closer to the standard than the high and low end. Check to see the stator plates on the drum spindle are fairly straight, and not bent like a butterfly at both ends.
 

·
Registered
Joined
·
1,128 Posts
Discussion Starter #24
The schematic can be found in older Book of Charts. 1980 perhaps. I can supply one if you like
I do not have any original chart books around... mostly just lose pages, and the old ones get purged....
It would be awesome if you could get me an original schematic!
Would you feel comfortable posting it on this thread for the community?

Also, how much of a technical adventure is it to do a proper calibration on a 919 with vacuum tubes?
Can it be done with a multi meter or is there more to it?
 

·
Registered
Joined
·
6 Posts
I do not have any original chart books around... mostly just lose pages, and the old ones get purged....
It would be awesome if you could get me an original schematic!
Would you feel comfortable posting it on this thread for the community?

Also, how much of a technical adventure is it to do a proper calibration on a 919 with vacuum tubes?
Can it be done with a multi meter or is there more to it?
When she is tuned properly, you should have a minimum point of 2 division or less with the needle, testing with a low wheat sample on the drum dial (around 10). After swapping tubes to find a good match, the next step would be adjusting the coil on the input terminal side of the chassis.
158285
 

·
Registered
Joined
·
346 Posts
My 919 quit (no needle movement). Pulled it apart and Power is getting to where it needs to but one of the tubes appears to have a brown burnt look on the end. Think it’s the tube that’s hooped. Where you get tubes?
 

·
Registered
Joined
·
3,990 Posts
Earlier in this thread, Anvil mentioned that the tubes are type DF92/1L4 and that he found a couple on E-bay. I'd look there first before going to farmtronics or desna. Odds are they get their tubes from the same place (E-bay) since tubes aren't exactly a current commodity.
 

·
Registered
Joined
·
1,128 Posts
Discussion Starter #29
My 919 quit (no needle movement). Pulled it apart and Power is getting to where it needs to but one of the tubes appears to have a brown burnt look on the end. Think it’s the tube that’s hooped. Where you get tubes?
Yes a Ebay search will get you the tubes you need, they're out there. I was able to find a matched set, new old stock from the American army. I think I paid $50 with shipping and all. Also a neighbour if mine ordered a pair for his 919 off e bay.
Its probably the quickest and easiest.
 

·
Registered
Joined
·
1,128 Posts
Discussion Starter #30
When she is tuned properly, you should have a minimum point of 2 division or less with the needle, testing with a low wheat sample on the drum dial (around 10). After swapping tubes to find a good match, the next step would be adjusting the coil on the input terminal side of the chassis.
View attachment 158285
Thanks for that!

Another question... what are the 2 set screw adjustments beside each vacuum tube??

And what do you mean by swapping tubes to find a good match? Just swapping side to side?
 

·
Registered
Joined
·
123 Posts
I switched from the old 919 to the automated 919 unit and it is a piece of crap, it is a year old and the front panel screwed up on it, sent it in for replacement and had it recalibrated two weeks ago and found out yesterday that it is out by 1% moisture. Don't waste your money on the new one, luckily I have dad's old 919 that I will get recalibrated and watch for the automated 919 to go up for sale at a RB timed auction this summer.
 

·
Registered
Joined
·
6 Posts
Thanks for that!

Another question... what are the 2 set screw adjustments beside each vacuum tube??

And what do you mean by swapping tubes to find a good match? Just swapping side to side?
The set screw adjustment is for the oscillator settings. Usually the one closest to the input is adjusted to set the null cap position. The second adjustment is for the reference and should be left alone. Swapping tubes side to side might perform better as well. I used 1T4 tubes as well...
 
21 - 32 of 32 Posts
Top