Help with 7536A-1 and a 8 pin IC with no numbers

  • Thread starter Thread starter in4sit4u
  • Start date Start date
  • Tags Tags
    Ic Numbers Pin
Click For Summary

Discussion Overview

The discussion revolves around identifying and replacing components in a circuit that produces police siren sounds. Participants explore the specifics of a transistor labeled 7536A-1 and an unidentified 8-pin integrated circuit (IC) with no markings. The conversation includes inquiries about the circuit's design and potential alternatives for repair or replacement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks help identifying a transistor labeled 7536A-1 and an 8-pin IC with no identifying numbers.
  • Another participant suggests that the 7536 could refer to a CMOS microcomputer and proposes that the 8-pin IC might be a dual TTL to CMOS driver.
  • Some participants recommend searching for a schematic or additional identifying information on the circuit board to aid in component replacement.
  • There is speculation that the unidentified IC could be a microcontroller, which may complicate replacement if it is programmed with proprietary code.
  • One participant mentions the possibility of the transistor being an NPN type based on its pin configuration.
  • Another participant discusses testing the transistor using a digital multimeter to determine its type and functionality.
  • Suggestions are made regarding the feasibility of building a simple circuit to replicate the siren sounds if the original cannot be repaired.
  • Participants discuss the common practice of manufacturers grinding off IC numbers to prevent easy duplication of circuits.
  • One participant notes that only five of the eight pins on the IC appear to be used, providing a description of the connections for each pin.

Areas of Agreement / Disagreement

There is no consensus on the exact identification of the components, and multiple competing views regarding the nature of the IC and the transistor persist throughout the discussion. Participants express uncertainty about the functionality and replacement of the components.

Contextual Notes

Limitations include the lack of identifying information on the IC and the potential for proprietary programming in the microcontroller, which may hinder repair efforts. The discussion also reflects varying levels of experience among participants in electronics.

Who May Find This Useful

Individuals interested in electronics repair, hobbyists working with circuits, and those seeking to understand component identification and replacement in similar applications may find this discussion beneficial.

in4sit4u
Messages
10
Reaction score
0
I am trying to replace some pieces in a circuit that produces police siren sounds and can't find new ones. one i believe is a transistor with the numbers 7536a-1 and an 8 pin IC with no numbers on it. Can someone please help me identify these. I am new to electronics and not real familiar with a lot of these items.
 
Engineering news on Phys.org
There is a CMOS microcomputer 7536 (42 pin I think) and an 8-pin 75361A dual TTL to CMOS driver. See www.datasheets4u.com[/URL] for datasheet searches. There is no 2N7536.
 
Last edited by a moderator:
in4sit4u said:
I am trying to replace some pieces in a circuit that produces police siren sounds and can't find new ones. one i believe is a transistor with the numbers 7536a-1 and an 8 pin IC with no numbers on it. Can someone please help me identify these. I am new to electronics and not real familiar with a lot of these items.

Welcome to the PF. Can you try to google for info about the circuit board itself? Does it have a name on it, or other numbers that might help to identify it? If you can get a schematic off the web, that will help you a lot in trying to do any component replacements. Especially if one IC has been black-topped (painted to conceal the original identifying info).
 
There are no numbers on the ic chip itself, nor are there any numbers on the board. If anyone can tell me how to post a pic of the board i will do that. it consist of the ic chip whick has 8 pins another 3 pin that looks like a transistor and has the numbers 7536A-1 on it. then it has 3 caps, one 100uf and 2 104 disk caps and that is it.
 
The little black-topped chip might be a simple microcontroller. In which case, you'd need the program inside the uC in order to duplicate it. If the developer was smart, they used "Secure" at the end of programming their uC, so that others could not easily reverse-engineer their work.

Which brings up the question -- why are you trying to duplicate this board?
 
No just repair it. i think i burnt up the ic, not really sure all i know is it won't work anymore. i have already replaced the parts i know only thing left to replace is the 2 parts i mentioned.
 
in4sit4u said:
No just repair it. i think i burnt up the ic, not really sure all i know is it won't work anymore. i have already replaced the parts i know only thing left to replace is the 2 parts i mentioned.

Where did you get it from originally? If that's a black-topped uC, you probably won't be able to fix it.

BTW -- have you tried beeping out the "transistor" to see if it's okay or blown? Have you tried drawing a schematic from the PCB itself? That might ttell you more about the circuit (like, what type of transistor it is).
 
i can draw you a pic of the entire circuit board if you want, it only has 5 parts total. It came in a model police car i bought off ebay.
 
i think the transistor is a npn because the middle leg is connected to the positive power lead.
 
  • #10
no really sure like i said I am new at this electronics stuff.
 
  • #11
in4sit4u said:
i think the transistor is a npn because the middle leg is connected to the positive power lead.

The common jelleybean discrete transistors that I'm used to using have these pinouts in TO-92 (small plastic) packages, read left-to-right:

2N3904 NPN:EBC

2N3906 PNP:EBC

2N2222 NPN: EBC

So having the middle leg connected to the + supply wouldn't be right for these particular transistors.
 
  • #12
the numbers on the three leg transistor show 7536A-1 but i can't find any info on this anywhere
 
  • #13
in4sit4u said:
the numbers on the three leg transistor show 7536A-1 but i can't find any info on this anywhere

Does your DVM have a "diode test" setting on it? If so, try beeping the trransistor out to figure out if it is an NPN or PNP. Worst case you can unsolder it from the PCB to get full access to the pins without other circuitry hooked onto them (which can confuse your diode test beeping).

If your DVM doesn't have a diode test setting, you can generally still use a simple resistance measurement instead. Measure between each set of 2 pins, checking both polarities.
 
  • #14
The siren does 4 different tones, if I can't find a way to fix this one is it possible to build a very simple circuit that will do the same thing. not real good with electronics but am willing to give it a try if someone can help i wopuld appreciate it.
 
  • #16
Hey, check out one of those pictures:

http://www.cpcares.com/media/CK015.jpg

Looks a lot like what you are describing -- an 8-pin DIP IC and a TO-92 transistor, with a couple of discretes. If you can read the writing on top of the IC (I'm not able to), that might give you one of your answers.

Maybe see if there is kit information for that board, if it looks similar to yours. Might be based on the same root design.
 
  • #17
This is a bit of a guess, but does the IC have the power going to two pins that are diagonally opposite each other in two of the corners? These would have a track going between them on the printed circuit board. Or, at least, does the + supply go to pin 8?
And does it have pin 1 going to the negative supply? This is unusual among chips.

The most likely chip someone would use in a siren could be a 555.
see this site:
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
No siren there, but info on 555 chips.

It is very common for producers of circuits to grind the numbers off so nobody can easily copy the circuit.

Testing the transistor is easier. If you have a digital multimeter look for a diode mode. Test the pins of the transistor (in circuit for a start) for conduction one way but not the other. One of the pins, (the base) should conduct to both other pins in one direction but not the other.
If any of the pins conduct very well in both directions, the transistor may be faulty and should be tested again out of circuit.
Testing in OHMS mode usually will not work because the meter tests at a low voltage which won't turn the diode junction on.
Exact replacement of the transitor probably isn't necessary and anything NPN would be worth a try.

If you are going to replace the two most expensive things on the board, maybe you should just rebuild the whole thing from new parts?
 
Last edited by a moderator:
  • #18
i want to thank everyone for the help. I can't find my exact siren but i have found a few kits online that i can just buy and replace mine. again thanks for all the help. if i find out anything about this circuit i will post and let you know.
 
  • #19
only 5 of the 8 pins appear to be used, 3 of them are not even soldered in. Pins 1,3 and 4 are not even used. pin 2 goes to a wire on the switch, pin 5 goes to ground, pin 6 goes to a speaker wire, pin 7 runs through the positive side of the 2 caps and one of the outer pins on the transistor i believe it is the c pin, pin 8 hooks to the other speaker wire. if this helps please let me know
 
Last edited:

Similar threads

Soldering small pins on IC to a board
  • · Replies 24 ·
Replies
24
Views
5K
Help me breadboard my circuit
  • · Replies 10 ·
Replies
10
Views
2K
Charlieplexing: LEDs have different brightness
  • · Replies 14 ·
Replies
14
Views
2K
Why Does the Filament Box in a CRT Electron Gun Have Multiple Pins?
  • · Replies 12 ·
Replies
12
Views
2K
What Does Tie Pin 1 High to Enable the Output Mean in Electronics?
  • · Replies 5 ·
Replies
5
Views
2K
Understand the Current Consumption of an IC in its Datasheet
  • · Replies 5 ·
Replies
5
Views
6K
Are my IC connections in my circuit correctly matching the pin out diagrams?
  • · Replies 4 ·
Replies
4
Views
4K
Connecting a 5 pin nte7077 voltage regulator
  • · Replies 3 ·
Replies
3
Views
3K
Seeking Heatsink for 8-Pin DIP IC
  • · Replies 6 ·
Replies
6
Views
8K
How To Remember IC Configurations?
  • · Replies 1 ·
Replies
1
Views
5K