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+--- Thread: Odd HP-35 Red Dot (/thread-9167.html)
Odd HP-35 Red Dot - aj04062 - 09-27-2017 11:55 PM
Well I picked up this Red Dot the other day. I am confident in saying this even though it looks like a V4 HP-35.
https://www.flickr.com/photos/155473427@N08/36652056184/in/dateposted-public/
SN is 1143A000364
https://www.flickr.com/photos/155473427@N08/37331046612/in/dateposted-public/
The ENTIRE front side has been replaced.
I had to inspect the inside to see what the board looked like.
https://www.flickr.com/photos/155473427@N08/37104866650/in/dateposted-public/
To my surprise it is an early board (note 03-72 date plus 1211 marking).
This older thread from a very early 35 had the same markings on the board.
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv020.cgi?read=212650
I guess this guy must've gone in for a major overhaul in '79 (see sticker on the CPU)
RE: Odd HP-35 Red Dot - jebem - 09-28-2017 12:15 PM
(09-27-2017 11:55 PM)aj04062 Wrote: Well I picked up this Red Dot the other day. I am confident in saying this even though it looks like a V4 HP-35.
...
To my surprise it is an early board (note 03-72 date plus 1211 marking).
It's always a pleasure to look to these machines internals and reconfirm the high quality of the 70's technologies.
Mine is not a red dot for sure.
Also it has got a PCB date code of 40 73, and one of the ROM ICs is marked with 7344 (1973 week 44):
http://4.bp.blogspot.com/-pyNvbIEGkAY/VCMFfreaCEI/AAAAAAAACKU/a1ETTh5g7eA/s1600/SAM_7888.JPG
But looking to your PCB, it seems that at least one of the ROM ICs is marked as "7303" (1973 week 03).
Would this still qualify it as a red dot?
Can you check if some of the ICs solder joints where manually re-soldered?
If yes, then probably someone have rebuilt it in 1979....
Edited to add this:
Does your machine have the famous "exp(ln(2.02) = 2" bug of the early firmware?
RE: Odd HP-35 Red Dot - aj04062 - 09-29-2017 09:56 PM
It is clear to me this went back for rework. I am guessing that the 7303 ROM was replaced to fix the "bug" which it does not have. The solder job on the board is excellent.
Before I removed the rear label, it does not look like it was ever molested.
(09-28-2017 12:15 PM)jebem Wrote:(09-27-2017 11:55 PM)aj04062 Wrote: Well I picked up this Red Dot the other day. I am confident in saying this even though it looks like a V4 HP-35.
...
To my surprise it is an early board (note 03-72 date plus 1211 marking).
It's always a pleasure to look to these machines internals and reconfirm the high quality of the 70's technologies.
Mine is not a red dot for sure.
Also it has got a PCB date code of 40 73, and one of the ROM ICs is marked with 7344 (1973 week 44):
http://4.bp.blogspot.com/-pyNvbIEGkAY/VCMFfreaCEI/AAAAAAAACKU/a1ETTh5g7eA/s1600/SAM_7888.JPG
But looking to your PCB, it seems that at least one of the ROM ICs is marked as "7303" (1973 week 03).
Would this still qualify it as a red dot?
Can you check if some of the ICs solder joints where manually re-soldered?
If yes, then probably someone have rebuilt it in 1979....
Edited to add this:
Does your machine have the famous "exp(ln(2.02) = 2" bug of the early firmware?
RE: Odd HP-35 Red Dot - Dave Frederickson - 09-29-2017 11:21 PM
(09-29-2017 09:56 PM)aj04062 Wrote: Before I removed the rear label, it does not look like it was ever molested.
I mucked up the label on my 35 forty years ago when I was a dumbass kid. Had to remove the screws under the label which hold the case together so I could see what was inside. Since then I've replaced the label with one from a donor.
So, Adam, how did you open the case without removing the label?
Dave
RE: Odd HP-35 Red Dot - aj04062 - 09-29-2017 11:53 PM
I remove the label with some heat from a spotlight and muscle. I then soak in iso alcohol to get the old adhesive off. Then roll to flatten out the wrinkles and lastly apply new 3M adhesive to the back.
(09-29-2017 11:21 PM)Dave Frederickson Wrote:(09-29-2017 09:56 PM)aj04062 Wrote: Before I removed the rear label, it does not look like it was ever molested.
I mucked up the label on my 35 forty years ago when I was a dumbass kid. Had to remove the screws under the label which hold the case together so I could see what was inside. Since then I've replaced the label with one from a donor.
So, Adam, how did you open the case without removing the label?
Dave
RE: Odd HP-35 Red Dot - Dave Frederickson - 09-30-2017 01:08 AM
(09-29-2017 11:53 PM)aj04062 Wrote: I remove the label with some heat from a spotlight and muscle. I then soak in iso alcohol to get the old adhesive off. Then roll to flatten out the wrinkles and lastly apply new 3M adhesive to the back.
Whoops! Past tense. I thought you were commenting on the condition of the label after you opened the case.
I was fortunate enough to have the adhesive on the donor label intact after removal. All I needed to do was smooth the label, moisten the adhesive with alcohol, and apply to the 35.
Dave