Odd HP-35 Red Dot

[aj04062]

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@...ed-public/
SN is 1143A000364
https://www.flickr.com/photos/155473427@...ed-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@...ed-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/...ead=212650

I guess this guy must've gone in for a major overhaul in '79 (see sticker on the CPU)

[jebem]

(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/VC...M_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?

[aj04062]

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/VC...M_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?

[Dave Frederickson]

(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

[aj04062]

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

[Dave Frederickson]

(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