ZX80 issue 3 no video no sync no IORQ

[mich]

Trying to get my ZX80 (Issue 3) to working again. I've put all except the ram chips on sockets. Tested the logic chips with a minipro2plus and replaced defective ones. All LS except IC 13, that's a S04N now, I couldn't get a LS version sofar. I replaced the cpu with a new Z84C0010 as I can't test easily the original z80. The 8332 I can read the first 2k of but not the rest as the minipro doesn't have the rom in its list. So I tested it as if a 2732 eprom. Which works for the first 2k addresses. The data is the same as the first 2k of the rom file I found. I assume (..) the rom is good.
When I measure signals, with my Hameg HM604 (allmost as old as the ZX80..) I see activity on the addressbus and databus of the Z80 but no IORQ (constant high). So no SYNC, so no video output.
Btw looking at signals at diffent places it all looks very noisy, no clean square signals what so ever.
The only chips I can't test or swap at all are the ram chips.
Anyone ideas? I'm a bit stuck here.

[1024MAK]

The SRAM chips are known to cause problems. One downside with both the ZX80 and ZX81 (and their clones) is that anything that messes up the execution of the code in the ROM (including faulty SRAM chips) will almost always result in no useful display.

Mark

[mich]

Thnx for the reply. Yes I was kind of afraid of that. I'll look into some way to connect a new (and thus bigger) ram chip.