Sega ram chip help

Hi I am going though my Sega mega cd motherboards I have a few with same faults I need
to find same or modern type ram ics

need to replace theses
HM514270AJ8 package type soj 40 can't find a datasheet
MB8464A-90L package sop 28
65256BLFP-10T

modern replacements would be ideal since would be Easer to find.

i have like 5 mega cd motherboards to replace these chips so they will come back to life.

all the best I hope someone can help me in the hunt for ram ic chips.

need them to be cheap as possible new would be best so may cost a little extra.

 

Last one is easy - it's just a 32k x 8 SRAM, and you can still get those.

Try http://www.renesas.eu/products/memory/low_power_sram/device/R1LP5256ESP-7SR.jsp

The MB8464A is a bit harder - it's a small device, and I don't think anyone still makes them.

The Sharp LH5164A-80 should work - it's still orderable, but I'm not sure any distributors stock it

The first one is going to a pain - it's a 256k x 16 bit DRAM @ 5V, and I don't think anyone has
made those for years. Probably your best bet is to look for NOS ones.

Here is the datasheet:

http://www.datasheetarchive.com/dl/Scans-030/ScansU9X14280.pdf

 

x

 

65256BLFP-10T = PSRAM, not SRAM.

That one is used for the Ricoh PCM chip and it being broken would not prevent the system from starting up.

We had that talk before Bart, and the problem with your MEGA-CD boards is broken traces, not faulty parts.

 

Yeah, but it's a PSRAM that was designed as a drop-in replacement for a 62256 type low-power SRAM. I suppose it's possible that the design is relying on the shorter in-page access time of PSRAM, but given how low all the clocks in a mega CD are, I somewhat doubt it. Even if it is, a 45ns SRAM is going to be faster on any access than the PSRAM is the current page.

 

I think SEGA used PSRAM because at the time it was cheaper than SRAM. (It also uses PSRAM in the original Mega Drive design as work RAM for the 68000....)

 

i did do a test i removed the HM514270AJ8 ic from other model one motherboard i get bios background and no boot animation so clearly i have found the fault on non booting consoles some do have bad traces not all of them ram chips do go bad.

if i do get these working i would be very happy i will do more research on these chips as for the

 

Ic 5 can be UPD424270-10 SOJ 40PIN still looking for this modern replacement.

 

That 40 PIN DRAM is specific for 68000 based systems (it has 2 8 bit banks with two read/write separated strobes).

 

if i remove ic 7 and 8 gives me white screen.

 

i would like to find replacement chips asap if l_oliveira can help me find a website or some where that stocks replacements if i can fix any of these you will get one l_oliveira and a jvc mech you needed.

 

Hi guys still need help on finding these chips.
i have been looking at lot of datasheets.

 

I found you request looking for SRAMS

I know the request was a while back, but..

I have some data sheets
for the hm514270
and hm514170
http://homepage.ntlworld.com/d_m.bright/PDF/hm514270.pdf


I may have some of these. I think they are used in the Arcade Model 2/2A/B/C PCB's

 

Don't know if this will help.. MB8464A (15L?)
http://www.aliexpress.com/item/Free...-FUJITSU-SOIC-Package-MB8464A/2041024684.html

 

Utsource is another good site to look up obscure ICs.