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Any HP-25c schematics?
08-31-2018, 01:14 PM
Post: #1
Any HP-25c schematics?
Hello everyone,

I've bought a "cheap" but heavily blue-white-green corroded HP-25c and washed and cleaned it. It was so damaged that in the wash process I almost lost a component; this the "big" black transistor on the left of the first (mid) RAM chip (thank you, Harald!):

[Image: 25chrrvg.png]

Now, I have to test it (and every component I guess) and to solder it (or a new one) on the board again. But where does it connect onto the board? I didn't find any picture or schematic neither in this site, nor on the PPC DVD of Jack Schwartz.

Any help will be appreciated.
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08-31-2018, 01:53 PM
Post: #2
RE: Any HP-25c schematics?

.pdf  Woodstock HP-21 HP-25 Schematics.pdf (Size: 1.21 MB / Downloads: 121) I've attached an ancient PDF that I had lurking around - hope that might help?
I've also got a NASA HP-25 program listing for calculating Loran time differences if you want to run and see if it works ok after your major trauma surgery on the calculator.
Dennis

Denny
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08-31-2018, 03:08 PM
Post: #3
RE: Any HP-25c schematics?
Great, many thanks!
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08-31-2018, 05:21 PM
Post: #4
RE: Any HP-25c schematics?
If you want to see the last photo in whole go to the website that is shown in the pdf. So you can see the whole hardware displayed.
Andi
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08-31-2018, 07:53 PM
Post: #5
RE: Any HP-25c schematics?
(08-31-2018 01:53 PM)Leviset Wrote:  … a NASA HP-25 program listing for calculating LORAN time differences …

Can be downloaded from archive.org as NTRS-1978002312 LORAN Time Difference.

BEST!
SlideRule
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09-01-2018, 04:17 AM
Post: #6
RE: Any HP-25c schematics?
(08-31-2018 07:53 PM)SlideRule Wrote:  Can be downloaded from archive.org as NTRS-1978002312 LORAN Time Difference.

Thanks for the link to the program.

These formulas are used:

\(
\begin{align*}
\beta_T&=\tan^{-1}[C\tan(\Phi_T) ] \\
\beta_R&=\tan^{-1}[C\tan(\Phi_R) ] \\
X &= \cos^{-1}[\sin(\beta_R)\sin(\beta_T)+\cos(\beta_R)\cos(\beta_T)\cos(\lambda_R-\lambda_T)]
\end{align*}
\)

But we can factor out \(\cos(\beta_R)\cos(\beta_T)\) and get:

\(X = \cos^{-1}[\cos(\beta_R)\cos(\beta_T)(\tan(\beta_R)\tan(\beta_T)+\cos(\lambda_R-\lambda_T))]\)

Hence we can avoid calculating \(\sin(\beta_R)\) and \(\sin(\beta_T)\) since \(\tan(\beta_R)\) and \(\tan(\beta_T)\) have already been computed.

This makes the program a bit shorter:
Code:
01: 24 06    RCL 6          C
02: 24 01    RCL 1          Φ_T                 C
03: 14 06    f tan          tan(Φ_T)            C
04:    61    ×              C tan(Φ_T) = tan(β_T)
05:    31    ENTER          tan(β_T)            tan(β_T)
06: 15 06    g tan⁻¹        β_T                 tan(β_T)
07: 14 05    f cos          cos(β_T)            tan(β_T)
08: 24 06    RCL 6          C                   cos(β_T)            tan(β_T)
09: 24 03    RCL 3          Φ_R                 C                   cos(β_T)            tan(β_T)
10: 14 06    f tan          tan(Φ_R)            C                   cos(β_T)            tan(β_T)
11:    61    ×              C tan(Φ_R)          cos(β_T)            tan(β_T)            tan(β_T)
12:    31    ENTER          tan(β_R)            tan(β_R)            cos(β_T)            tan(β_T)
13:    22    R↓             tan(β_R)            cos(β_T)            tan(β_T)            tan(β_R)
14: 15 06    g tan⁻¹        β_R                 cos(β_T)            tan(β_T)            tan(β_R)
15: 14 05    f cos          cos(β_R)            cos(β_T)            tan(β_T)            tan(β_R)
16:    61    ×              cos(β_R)cos(β_T)    tan(β_T)            tan(β_R)            tan(β_R)
17:    22    R↓             tan(β_T)            tan(β_R)            tan(β_R)            cos(β_R)cos(β_T)
18:    61    ×              tan(β_R)tan(β_T)    tan(β_R)            cos(β_R)cos(β_T)    cos(β_R)cos(β_T)
19:    21    x<>y           tan(β_R)            tan(β_R)tan(β_T)    cos(β_R)cos(β_T)    cos(β_R)cos(β_T)
20:    22    R↓             tan(β_R)tan(β_T)    cos(β_R)cos(β_T)    cos(β_R)cos(β_T)    tan(β_R)
21: 24 04    RCL 4          λ_R                 tan(β_R)tan(β_T)    cos(β_R)cos(β_T)    cos(β_R)cos(β_T)
22: 24 02    RCL 2          λ_T                 λ_R                 tan(β_R)tan(β_T)    cos(β_R)cos(β_T)
23:    41    -              λ_R-λ_T             tan(β_R)tan(β_T)    cos(β_R)cos(β_T)
24: 14 05    f cos          cos(λ_R-λ_T)        tan(β_R)tan(β_T)    cos(β_R)cos(β_T)
25:    51    +              tan(β_R)tan(β_T)+cos(λ_R-λ_T)           cos(β_R)cos(β_T)
26:    61    x              cos(β_R)cos(β_T)(tan(β_R)tan(β_T)+cos(λ_R-λ_T)) = cos(X)
27: 15 05    g cos⁻¹        X
28: 24 05    RCL 5          A(rad)  X
29:    61    ×              d = AX
30:    74    R/S            d
31: 24 00    RCL 0          T_m   T_s
32:    41    -              T_s-T_m

Example

21282.339
π
×
180
÷
STO 5

0.99664767
STO 6

39.1930
→H
STO 3

82.0615
→H
STO 4

34.034604
→H
STO 1

77.544676
→H
STO 2

f CLEAR PRGM
R/S

2317.7679


Cheers
Thomas
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06-17-2019, 06:14 PM
Post: #7
RE: Any HP-25c schematics?
(08-31-2018 01:53 PM)Leviset Wrote:  I've attached an ancient PDF that I had lurking around - hope that might help?
I've also got a NASA HP-25 program listing for calculating Loran time differences if you want to run and see if it works ok after your major trauma surgery on the calculator.
Dennis

Sadly, Jaques’ site, while excellent, is on the 21 and 25, but not the 25c. While there is much relevant information, the original question seems to still be unanswered: Is there a schematic for the 25c available? Thanks.-kby
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06-17-2019, 06:40 PM
Post: #8
RE: Any HP-25c schematics?
Did you look at Tony's schematics? HP25C included ...
https://www.hpmuseum.org/forum/thread-13065.html
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06-17-2019, 07:12 PM
Post: #9
RE: Any HP-25c schematics?
(06-17-2019 06:40 PM)AndiGer Wrote:  Did you look at Tony's schematics? HP25C included ...
https://www.hpmuseum.org/forum/thread-13065.html

Mea culpa. I had, but apparently not carefully enough. I think maybe I got an earlier version, or the name "Classic Schematics" stuck in my mind, although I did know he subsequently added the 19c and 29c.-kby
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