Which new model can be used to replace the RAM chip - Page 1
Forum section: electronics / projects

author: daisizhou
author_rank: Super Contributor
timestamp: August 14, 2023, 09:18:07 pm
content: Hello everyone.I came across an old-fashioned circuit board,The circuit uses an old-fashioned RAM chip model of LH5160HD,It has been discontinued for many years and is currently difficult to purchase. I would like to know which RAM chip can replace it.If you know, please let me know. Thank youThe main chip is MC68HC11G5FN，The eeprom chip is 27C010, currently using 27C1001 as an alternative,PAL chip uses 22V10Z,X24C16P is also an EEPROM used to store calibration data.

author: Benta
author_rank: Super Contributor
timestamp: August 14, 2023, 09:34:35 pm
content: Seems to be a 16k x 8 asynchronous SRAM, which is an oddball size. Could be easily replaced by a 32k x 8 (tying the upper address line to ground), which is a much more common size and readily available. But check the pinout to be certain.https://www.issi.com/US/product-asynchronous-sram.shtml(IS62C256AL)

author: Shonky
author_rank: Frequent Contributor
timestamp: August 14, 2023, 09:48:57 pm
content: Quote from: Benta on August 14, 2023, 09:34:35 pm15 bits is 32k x 8. In fact the schematic shows a 128k x 8 part with the upper two address lines tied low.Some likehttps://www.digikey.com.au/en/products/detail/alliance-memory-inc/AS6C1008-55PCN/4234576Would be very close to drop in. Check speeds etc.

author: Benta
author_rank: Super Contributor
timestamp: August 14, 2023, 09:53:26 pm
content: Quote from: Shonky on August 14, 2023, 09:48:57 pmYo're right, my mistake. I counted 14 active address lines (old eyes).Well, then 32k x 8 it is.(Oh, and thanks for reminding me of Alliance. I'd forgotten about them).

author: daisizhou
author_rank: Super Contributor
timestamp: August 14, 2023, 11:14:14 pm
content: Thanks.It seems that AS6C1008 can be perfectly replaced.I mean, all pin definitions are usable,Simply remove the chip and install a new one.The only thing I have some doubts about is pin 30,On the schematic diagram, the 30th pin of LH5160 is connected to a high level,The 30th pin of AS6C1008 is CE2

author: Shonky
author_rank: Frequent Contributor
timestamp: August 14, 2023, 11:17:13 pm
content: Something doesn't quite compute here. LH5160 appears to be a 8k x 8 SRAM from SHARP in a 28 pin package?Pin 30 is active high. So wiring it high is fine. Then only the active low CE# on pin 22 is in play. Both need to be active for the chip to be enabled.So this is a QA45?

author: daisizhou
author_rank: Super Contributor
timestamp: August 14, 2023, 11:25:30 pm
content: Yes, QE-45analyzer,I plan to remake it.I checked the manual and found that LH5160HD is labeled with DIP32 packaging

author: daisizhou
author_rank: Super Contributor
timestamp: August 15, 2023, 03:52:42 am
content: Can I use AS6C1008 to replace LH5160?Because few sellers sell the LH5160 chip

author: Shonky
author_rank: Frequent Contributor
timestamp: August 15, 2023, 07:13:03 am
content: Quote from: daisizhou on August 15, 2023, 03:52:42 amI think so, and said as much.Do you have a picture of a board or anything else?Where are you going to get the firmware from?

author: daisizhou
author_rank: Super Contributor
timestamp: August 15, 2023, 07:31:36 am
content: I obtained the firmware from a friend,Above is an internal image of his console,What confuses me is that his EEPROM chip is 27C1001, but the model number originally listed in the data manual is 27C010,And I didn't find any RAM chips in the physical pictures

author: Shonky
author_rank: Frequent Contributor
timestamp: August 15, 2023, 07:50:44 am
content: The RAM may not be needed? It appears the schematic you have is not for the exact same board. The service manual from a quick google appears to have all blank schematic pages. Where did you get the schematic from?That HC11 only has a small amount of RAM but maybe the final product can get by on that?What about the PAL? If it has its security bit set, how will program that?27C1001 is same enough as a 27C010 once programmed. Manufacturers probably hadn't quite come up with a naming scheme when rolling over at 1Mbit. What's the problem with that? Even the schematic says both part numbers? A simple Google will explain.

author: Shonky
author_rank: Frequent Contributor
timestamp: August 15, 2023, 07:54:15 am
content: I can see the schematic in the PDF you linked after editing your post. It seems IC14 and IC16 occupy the same location/footprint somehow from the layout.I think you need to investigate yourself more. You can't expect someone without access to a working unit to figure it out.The schematics refer to AR095. Your board is AR099.Perhaps the SRAM is surface mount under the EPROM? Seems unlike given nothing else is SMT.

author: daisizhou
author_rank: Super Contributor
timestamp: August 15, 2023, 08:09:17 am
content: yes IC14 looks like it's under IC16,But from the overall analysis, all the chips are packaged in DIP, and the possibility of RAM chip SMT package is not very great.And the first part of the schematic "PROCESSOR BOARD"，IC2 and IC3 power and negative poles are not marked,IC6 does not mark the exact modelAR099 may be a modified version in 1999Looks like I still have a lot of doubts to confirm

author: daisizhou
author_rank: Super Contributor
timestamp: August 15, 2023, 08:14:45 am
content: The 30th pin of 27C1001 is NA, while the 30th pin of 27C010 is A17, which is connected to the 15th pin of IC15，If 27C1001 is used to replace 27C010, then the 30th pin becomes NA. What is the practical significance of connecting it to the 15th pin of IC15?

author: Shonky
author_rank: Frequent Contributor
timestamp: August 15, 2023, 08:34:49 am
content: There's no A17 in a 1 megabit device. You need to cross reference the pins yourself. It's probable they are doing some paging in the EPROM.