TMP87CH36N3292 Alternative(s)

[xibalban]

Hello folks,

So I have an old CRT TV with this Toshiba Chip TMP87CH36N, which is a micro-controller. The chip has gone bad (shorted) and needs to be replaced. However, I can find no seller for it, nowhere. Hence, I wrote to Toshiba and they responded by saying that the chip is obsolete and no longer available.

I wanted to revive my TV still, so does anyone know if there are any replacement chips that I could use instead of the TMP87CH36N3292 (give me fish), or guide me how to find alternative/equivalent replacement chips (teach me how to fish). The datasheet for the chip in question is attached here ->> https://cdn.datasheetspdf.com/pdf-down/T/M/P/TMP87CH36_ToshibaSemiconductor.pdf.<<-

Thanks and stay safe fellas!!

[DrG]

https://www.ccfloffer.com/tmp87ch36n-3292-chip-viewdetails8793.html

[xibalban]

https://www.ccfloffer.com/tmp87ch36n-3292-chip-viewdetails8793.html

You are Beautiful!! Thank you.

PS: Just curious, what if a situation arises where you need to replace an obsolete chip like mine? How do we find an active match? Is that even possible, I know it is possible with transistors.

[amyk]

It is a microcontroller, so if you can't find the original part, you will need to reverse-engineer what it controls and write the corresponding code to perform the same function using a currently available part.

Note that since it uses mask ROM, you will need to find a replacement part with the same ROM contents as the original.

[DrG]

https://www.ccfloffer.com/tmp87ch36n-3292-chip-viewdetails8793.html

You are Beautiful!! Thank you.

PS: Just curious, what if a situation arises where you need to replace an obsolete chip like mine? How do we find an active match? Is that even possible, I know it is possible with transistors.

Many times one is SOL Also, note what @amyk said about the ROM. A quick browse of the data sheet indicates that it certainly does have on board ROM and, more than likely, it has been programmed. IOW just putting a new one on the board is unlikely to do anything good. Welcome to SOL land But good luck.

[xibalban]

Well, when I look at the full circuit diagram of the TV, I find a separate EEPROM present on board which has been interfaced with the µController. Is it possible that the microcontroller doesn't actually use its in-bulit rom (of 16 KB in this case)?

I know that only the TV manufacturer will be able to give me a definitive answer, but any wild guesses guys? I have attached the relevant circuit diagram of the TV, check it out.

Thank you. [ Specified attachment is not available ]

[srb1954]

Well, when I look at the full circuit diagram of the TV, I find a separate EEPROM present on board which has been interfaced with the µController. Is it possible that the microcontroller doesn't actually use its in-bulit rom (of 16 KB in this case)?

I know that only the TV manufacturer will be able to give me a definitive answer, but any wild guesses guys? I have attached the relevant circuit diagram of the TV, check it out.

Thank you. (Attachment Link)

The EEPROM is quite small, only 1kBytes, so it isn't large enough to contain much of a useful program.

It is likely provided for storage of setting parameters as selected by the user e.g. last channel selected

[xibalban]

Well, when I look at the full circuit diagram of the TV, I find a separate EEPROM present on board which has been interfaced with the µController. Is it possible that the microcontroller doesn't actually use its in-bulit rom (of 16 KB in this case)?

I know that only the TV manufacturer will be able to give me a definitive answer, but any wild guesses guys? I have attached the relevant circuit diagram of the TV, check it out.

Thank you. (Attachment Link)

The EEPROM is quite small, only 1kBytes, so it isn't large enough to contain much of a useful program.

It is likely provided for storage of setting parameters as selected by the user e.g. last channel selected

Your response was quick, and you're right. I was actually about to modify my post with this correction, but thanks anyways. EEPROM actually stores my last channel, volume, brightness settings, etc., and has no connection to the actual µController program. I will write to Philips, asking them for the program code so that I can burn it into the new chip that I'm planning to buy. Let's see how they respond.

Would the TV work (or turn on at least, which it isn't at the moment), if I exclude the µController circuit. I could cut the supply rails to the chip and see eh. It runs on 5 V DC which is shorted right now (as the chip is shorted). My bad, I haven't isolated the fault and tried plugging the TV back.

[srb1954]

Your response was quick, and you're right. I was actually about to modify my post with this correction, but thanks anyways. EEPROM actually stores my last channel, volume, brightness settings, etc., and has no connection to the actual µController program. I will write to Philips, asking them for the program code so that I can burn it into the new chip that I'm planning to buy. Let's see how they respond.

Would the TV work (or turn on at least, which it isn't at the moment), if I exclude the µController circuit. I could cut the supply rails to the chip and see eh. It runs on 5 V DC which is shorted right now (as the chip is shorted). My bad, I haven't isolated the fault and tried plugging the TV back.

I wouldn't expect anything much to work without the microcontroller in circuit. It probably controls nearly every function of the TV e.g selecting signal sources, tuning to a channel, controlling audio paths and levels.

[amyk]

Upon further inspection, the 3292 might be the mask ROM ID - in which case if you do get a new (old stock, likely) one, it should be the same.

Since it's mask ROM, you can't simply get the code (if Philips will even give it to you...) and "burn it into the new chip".

[xibalban]

Upon further inspection, the 3292 might be the mask ROM ID - in which case if you do get a new (old stock, likely) one, it should be the same.

I see. I'm learning new things everyday here. So the chip is TMP87CH36N (blank Chip) and this same chip with a masked rom pre-built-in will have a suffix with the ROM ID. Cool, thank you. So, that means what @DrG pointed out to here

https://www.ccfloffer.com/tmp87ch36n-3292-chip-viewdetails8793.html

is actually the chip with the ROM already burnt in, right?

Since it's mask ROM, you can't simply get the code (if Philips will even give it to you...) and "burn it into the new chip".

So,  how are "masked ROMs" burnt? Do you imply that they are not re-programmable?
By the way, I have already written to Philips, let's see how they respond.

[srb1954]

So,  how are "masked ROMs" burnt? Do you imply that they are not re-programmable?
By the way, I have already written to Philips, let's see how they respond.

Mask ROM chips used to be made by adding final metal layer on top of the silicon chip which made the appropriate electrical connections between the transistors on the chip to form the desired S/W code within the program execution memory of the microprocessor. This layer was patterned on to the chip using a photographic exposure mask hence the term "mask ROM". After the custom code is "masked" onto the silicon chip it is packaged as for a standard chip and then custom marked with the customer's part number.

Since this process was done as part of the main silicon chip manufacturing process it wasn't economically viable for small production quantities or amenable to changes or fast turn-around times. Nowadays mask ROM devices are usually one-time programmable EPROM or flash memory devices that can have the S/W code burned into them by the chip manufacturer after the normal silcon chip production and packaging processes. This has the advantage of greater flexibility allowing smaller order quantities and faster turn-around times in the event of S/W changes. The disadvantage is that the extra handling and time for the programming process adds to the cost.

True mask ROM devices may still be manufactured today but these will only found for stable products manufactured in vast quantities where the component cost must be kept to the lowest possible.

[xibalban]

So,  how are "masked ROMs" burnt? Do you imply that they are not re-programmable?
By the way, I have already written to Philips, let's see how they respond.

Mask ROM chips used to be made by adding final metal layer on top of the silicon chip which made the appropriate electrical connections between the transistors on the chip to form the desired S/W code within the program execution memory of the microprocessor. This layer was patterned on to the chip using a photographic exposure mask hence the term "mask ROM". After the custom code is "masked" onto the silicon chip it is packaged as for a standard chip and then custom marked with the customer's part number.

Since this process was done as part of the main silicon chip manufacturing process it wasn't economically viable for small production quantities or amenable to changes or fast turn-around times. Nowadays mask ROM devices are usually one-time programmable EPROM or flash memory devices that can have the S/W code burned into them by the chip manufacturer after the normal silcon chip production and packaging processes. This has the advantage of greater flexibility allowing smaller order quantities and faster turn-around times in the event of S/W changes. The disadvantage is that the extra handling and time for the programming process adds to the cost.

True mask ROM devices may still be manufactured today but these will only found for stable products manufactured in vast quantities where the component cost must be kept to the lowest possible.

That was very informative. Thank you very much. So, in essence, the chip in question may not be available in its un-programmed state (i.e. without a mask ROM), I guess. I think I will just gamble with my $30 (since the minimum order is 5 pcs) and buy it off the online store.

There was no response from Philips whatsoever, so far. Have a great Sunday fellas and thank you everyone.

[DrG]

That was very informative. Thank you very much. So, in essence, the chip in question may not be available in its un-programmed state (i.e. without a mask ROM), I guess. I think I will just gamble with my $30 (since the minimum order is 5 pcs) and buy it off the online store.

There was no response from Philips whatsoever, so far. Have a great Sunday fellas and thank you everyone.

Please do let us know what happens.

I was happy to post that link that I found, but I don't know much else that might be useful - especially not what that -3292 suffix means (I did look for a while). I also have no idea what else on your board could be damaged 

I learned from the thread and hope you hit some luck with that vendor.

[xibalban]

That was very informative. Thank you very much. So, in essence, the chip in question may not be available in its un-programmed state (i.e. without a mask ROM), I guess. I think I will just gamble with my $30 (since the minimum order is 5 pcs) and buy it off the online store.

There was no response from Philips whatsoever, so far. Have a great Sunday fellas and thank you everyone.

Please do let us know what happens.

I was happy to post that link that I found, but I don't know much else that might be useful - especially not what that -3292 suffix means (I did look for a while).

I learned from the thread and hope you hit some luck with that vendor.

I'll surely will update this thread with new developments, on the chip procurement as well on any updates from Philips. You are right, this has been a great learning experience for me as well about "mask ROMs". Thank you for the link to the online store.

I also have no idea what else on your board could be damaged 

Well, the board had no problems to start with. The flyback transformer had insulation breakdown and started to generate sparks (between its body and its HV cable). The TV was still working, with the audible intermittent sparks of course. I found a replacement transformer and replaced it but the TV died again in a few days. Upon inspection, I found that the HOT (Horizontal Output Transistor) had blown off, so I replaced that too. After a few weeks, it stopped again and this time the power supply MOSFET had blown. I got an equivalent replacement and replaced it, along with the bridge rectifier and a few capacitors that had been shorted. The power supply section was repaired and I managed to get all the secondary DC voltages except for the +5 V for the microcontroller (and the TV wouldn't start), which was when I found that the chip had been shorted. Since I invested a lot of time and replaced quite a lot of components on the TV (and learned a lot during the process), I couldn't let it simply go to the dumpster. You already know the rest of the story. 

[xibalban]

UPDATE: Philips responded by saying that the said chip is no more supported and has become obsolete.

End of my short CRT story.

[amyk]

The fact that you managed to even get a response from Philips is surprising.
Most consumer electronics companies will simply ignore people asking them for parts.

[xibalban]

The fact that you managed to even get a response from Philips is surprising.
Most consumer electronics companies will simply ignore people asking them for parts.

Well, Philips has always responded to my requests (is that unusual?). Last time, I requested for the schematic of the same TV and they guided me to their service centre, whence I was able to grab a copy.