Two sets of pics attached.

What is the white device in the first set of pics? And, what do the "3.8" and "7.5" on it indicate/mean? It's from a mid-90s car circuit board (that enables the shift lever to be moved out of Park on an AT when the brake pedal is pushed and the key is in the Ign). Under the device (on the top of the board) it says "R17,R18" (no spaces, exactly as written). At first, I thought it may have been a relay, but it doesn't look tall enough AND it has a non-smooth ceramic'y feel AND on the device's bottom there are 2 small rectangular cavities under each end - and possibly under the middle (can't see under the middle and can't get a good pic of the cavities).

Also, what is the 15-pin long thin black IC in the second set of pics? It's labelled "TH-1700A 9903" on the front. The board label is "HIC-1".
What does the "H" mean?
What company may have been TH?

Can't find anything on either of these devices.

Thanks.

 

The big white square is likely a 6,8 ohm resistor, maybe 5 watts.
The large black "thing" is a small printed circuit board with many parts on it. I cannot tell what it does.

 

Isn't that a hybrid integrated circuit with a thixotropic dip? I don't remember seeing one of those since the early 1980's. If you can find the service manual it might include a schematic of the circuit, though I am not sure how that would help you.

 

I believe that the HIC stands for Hybrid integrated circuit. This was a common thing years ago where subassemblies were sealed like this to make "ICs". These are manufacturer dependent and you are not likely to find them any more. On schematics, these were often shown just like ICs with no internal specifics.

The white part is likely a dual resistor since you have the board silkscreen shows R17,R18. If these are open, you can replace with 2 separate resistors if space will allow it.

 

Any insight as to why such a large size (device) for the dual resistors? Why hadn't they (just) used smaller resistors, like they did elsewhere on the board?

Any significance to the device having the ceramic-y feel to its outer case? What's likely inside the case that made it the design/electrical choice for the 2 resistors?

Would you think the 2 resistors are serving 2 different circuits, or might the 2 be used in series?

Do you think the 3.8 and 7.5 imprints are (just) the ohms of each resistor? And why would the 6.8 in black be the ohms (versus the imprinted #s)? Can you explain (what I'm missing)?

I presume I should NOT ohm the white device's legs to determine/confirm the resistors and their values (so I do NOT potentially damage other devices on the board, including the HIC). Is this correct? (I won't be removing the white device.)

Any insight to what the dip material would have been?

Thanks!

Oh, and I do have the SM, and you're correct, it doesn't give enough info for the HIC.

 

Look at the bottom side of the PCB. There may be broken solder joints. This happens with vibration and time. Look at the pins on the white connector and on any large part. They could all be reheated.

There are two parts with 3 legs. Probably a transistor and voltage regulator. They need to be tested.

The resistor can be tested with an ohm meter.

 

Possibly dual 6.8Ω high wattage ceramic resistors.

 

I have seen similar resistors that have a thermal switch built into them (4 legs total), One pair is the resistor, the other is the thermal switch. These are not common, but I've seen them in some commercial power supplies back in the 1980s to1990s
The thermal switch was to alert the supply if the current flow was too high (steady state), and heating the the resistor too much. Modern electronics now uses different methods.

 

@sagor
Interesting you say this, because there is a tiny graphic (I think??) under the white resistor device that, when I first spotted it, I thought was indicating a switch. However, I can barely see it enough to know ... and there is a similar subset graphic on the board elsewhere that got me wondering if the these were some sort of grid alignments in the manufacturing process. (The subset graphic didn't seem to be associated with any device.) I will try to build a simple picture of what the tiny graphic might be illustrating, and I'll post it. But, it'll take some time to do this. For now, I would just note the tiny graphic is a series of teeny vertical and possibly slanting lines - some of the vertical lines in parallel - with dots in between a couple of the teeny lines - if that helps or reinforces your insight.

Oh, and would the thermoswitch more than likely have been able to reset itself if/when the current flow backed off (with the board then being able to continue to operate) ... or would the thermoswitch serve to permanently disable the board?

 

@ronsimpson
I do intend to get to the Vreg and transistor (in your pics - thanks), but haven't gotten there quite yet.

All,
so ...
on the white resistor device, there is a series of pics attached below showing the symbols under the device. I happened to catch (notice) that 2 of the symbols appear elsewhere and appear to be the same (there): the arrow also is on the top left corner area and the rectangle with continuation header line is on the bottom left corner (making it diagonally opposite in location from the arrow and vice versa). However, there also are 2 slanted lines in between the arrow and rectangle (under the white resistor device), that I don't see anywhere else. See text-box details of these slanted lines in the far right pic.

Based on all this info/pics/details, should I presume the symbols under the white device are (were) for circuit board manufacturing alignments ... and not indicating a switch (resistor-thermoswitch) symbolization afterall?

Thanks.

Oh, and just to clarify the details in the far right pic, the left-slanted line does not touch anything - not the rectangle, nor arrow, nor right slanted line.

 

@sagor
Interesting you say this, because there is a tiny graphic (I think??) under the white resistor device that, when I first spotted it, I thought was indicating a switch. However, I can barely see it enough to know ... and there is a similar subset graphic on the board elsewhere that got me wondering if the these were some sort of grid alignments in the manufacturing process. (The subset graphic didn't seem to be associated with any device.) I will try to build a simple picture of what the tiny graphic might be illustrating, and I'll post it. But, it'll take some time to do this. For now, I would just note the tiny graphic is a series of teeny vertical and possibly slanting lines - some of the vertical lines in parallel - with dots in between a couple of the teeny lines - if that helps or reinforces your insight.

Oh, and would the thermoswitch more than likely have been able to reset itself if/when the current flow backed off (with the board then being able to continue to operate) ... or would the thermoswitch serve to permanently disable the board?

I don't know what kind of thermal switch I've seen, whether they fail permanently or just open (close) when hot. It was quite a while ago. Only the manufacturer would know for sure. I still have one of those resistors, but the thermal switch was removed (it was under some ceramic cement) and it is just a small cavity where the thermal device was, the rest of the resistor is just the regular white ceramic with 2 leads.

 

It might also be a current sensing resistor electrically similar to:
https://blog.mbedded.ninja/electron.../current-sensing-resistor-large-four-lead.jpg

A link to a PDF showing a 4 wire thermal resistor:
http://resistors.co.kr/board/bbs/download.php?bo_table=pro12&wr_id=5&no=3

or it could be electrically similar to these with thermal cutoff:

 

First, thanks to each of you who responded - @ronsimpson , @DickCappels , @abrsvc , @MrChips , and @sagor . Every comment helped. Second, as an update, the white device is a dual resistor (7.5 and 6.8, the 3.5 wasn't used), and is used individually and in series (on different circuits). This also means the special graphic under the dual resistor was not for the resistors (it was part of the manufacturing). And, the HIC manages the signals in the original post, activating the external solenoids. Again, thanks!