Baldwin DRO repair

Curious here, are the nixies the only tubes present? Some tubes were actually designed as logic devices and in fact the burned-out nixie could theoretically affect the device operation. Not that it should have been designed that way though. :)

you may find that you can sell the nixies for enough to buy a much newer (used) DRO, or to at least pay for the parts to replace the nixies with LED displays - Nixies are getting pretty dear. A simple diode matrix will turn the nixie drive into an LED drive (for example, from one pin per number to 7-segment), and you can adjust the power supply from 90V to 5V by a minimal amount of work (there may even be

5V already available, just rewire)

Bill

to contact me, do not reply to this message, instead correct this address and use it

will iam_ b_ No ble at msn daught com

It should be easy enough to reverse engineer the device. Also nixie tubes are 10 segements devices. One line for each digit. Mapping would be required as well as changing the supply voltage. Simon Shabtai Evan

William B Noble (d> you may find that you can sell the nixies for enough to buy a much

What is happening and what is not happening on the readout. Does it change when you move the slider? does it always read the same numbers no matter what is done? The old readouts are compariatively easy to fix. chips are cheap. Determine the general area of the problem and then change some chips in that area. If the reset doesnt reset some of the numbers, the drivers probably have a short or the input to the nixie drivers. Get an ECG book with the chip pinouts and check the logic on the chips... or just replace them one at a time.

John

No there's several dozen logic chips.

I didn't look for an exact replacement yet but all the nixies I saw online were in the $10-$20 range. Yeah I take them out and sell them if I knew I had a buyer but that is probably unlikely and I think they look cool anyway!

According to jabba :

I consider that highly unlikely. Nixies don't have a filament, and don't "burn out" as a result.

If the glass is cracked, it will no longer have a (partial) vacuum, and thus will not work.

It is far more likely to be the driver chips. Have you tried swapping the supposedly "burned out" Nixie with one which still lights up? I'll bet that the one which you considered burned out will light up in another socket, and the "good" one will not light in the other socket.

I have no schematics, and no experience with a Baldwin.

Good Luck, DoN.

Just a note on Nixie driver chips. Experiences from the 60's

Most I have seen are working right at their breakdown voltage when the element is off.

Most are open collector pull down outputs.

If you change chips install sockets if they are already present.

Details with chip numbers would help greatly. Pictures even better.

I don't recall ever having a Nixie fail, was always the driver.

Will help as much as I can online

Hugh

D> According to jabba :

It may well be the driver and not the nixie. All I know at this is that it doesn't work and I wrongly assumed it was the tube. The driver is an SN7441AN which is a TI chip and I'm having a hard time getting a data sheet.

Google: 7441 ttl "data sheet" "bcd to decimal" Second result (unicornelectronics) has a link to the data sheet. First result is worth reading for general background if you aren't a Nixie enthusiast.

I would expect a high voltage OC driver to fail shorted, but I belive you said the offending nixie wasn't lighting. I'd check if there is a

70 to 80V feed from the HT rail to that tube's anode via a limiting resistor which may well have failed open. 7441 & 7441A have NO blanking feature so should always show something on the Nixie if the tube and the chip are both getting power.

Alright... nixies aside for a moment... First thing I noticed is that the display changes when you move some of the thumb switches. (This unit has s thumb roller switch for each nixie so you can set each digit on the display. Then you press "Set" to send the selected numbers to the display.) The display should only change when the set button is pressed. I verified the output of one of the counter chips (SN74192N) was changing without pressing the set button with my logic probe. Then I verified that the LOAD line was not changing when the rollers were moved. This happens for three of the five counters. I think I may just replace them all. Your thoughts?

Alright... nixies aside for a moment... First thing I noticed is that the display changes when you move some of the thumb switches. (This unit has s thumb roller switch for each nixie so you can set each digit on the display. Then you press "Set" to send the selected numbers to the display.) The display should only change when the set button is pressed. I verified the output of one of the counter chips (SN74192N) was changing without pressing the set button with my logic probe. Then I verified that the LOAD line was not changing when the rollers were moved. This happens for three of the five counters. I think I may just replace them all. Your thoughts?

7441 is a BCD(4 bit) to decimal(10) decoder 7447 is a BCD to 7 segment decoder.

Where are you located as I may have some of them, will have to go deep into the archives to see tomorrow.

Hugh

Hi Hugh... I responded to a different post of yours. I will repost it here.

Alright... nixies aside for a moment... First thing I noticed is that the display changes when you move some of the thumb switches. (This unit has s thumb roller switch for each nixie so you can set each digit on the display. Then you press "Set" to send the selected numbers to the display.) The display should only change when the set button is pressed. I verified the output of one of the counter chips (SN74192N) was changing without pressing the set button with my logic probe. Then I verified that the LOAD line was not changing when the rollers were moved. This happens for three of the five counters. I think I may just replace them all. Your thoughts?