Component Equivalents/substitutions

DEATH · December 2006

A while ago, I mentioned to somebody in a thread that we should have a list of component equivalents and substitutions so that it's easier to fix our Spectrums. The following is a short list of all the substitutions I know work - either by direct observation of seeing it in a properly working Spectrum, or substituting the component myself and doing a 24 hour bench test.

If anybody has experience of other components working properly, please let me know so that I can compile a decent sized chart or something. It would help if the components are easy to get hold of in the USA and Europe, but not essential.

Foggy, if you think this is at all useful to you, you have implicit permission to use it in The Shed

Section in bold text: Updated info from a link kindly supplied by Steve Parry-Thomas. Thanks too, to Droy Trastero, author of the original site. Please note, this info untested by myself.

ZTX231 can be replaced with BC251, BC307, BC512, BC557
ZTX313 can be replaced with BC172, BC183, BC238, BC383
ZTX650 can be replaced with BC537, BC737, BC487, BC489, BC538
BC184 can be replaced with BC384, BC413, BC550

BA158 fast recovery diodes work in place of the BA157 issue 2+
ZTX650/651 works in place of ZTX450, TR7, Issue 3+
ZTX651 works in place of ZTX650 in TR4 position issue 2+
BC184 work in place of ZTX313 in TR8 - TR9 position issue 3+
ZTX750 will work in place of ZTX213 at position TR5 Issue 2+
ZTX313's in TR1/TR2 position can be replaced with BC547, BC548 and BC549 in Issue 2+ Usually improve picture quality significantly

MPS 2369 can be used in TR1, 2, 3 and 6 on issue 3B and
BC 549B in TR9 and TR8 on an issue 6A (Thanks Odious)

MM5920N (national Semiconductors) chips are equivalent to 4116 RAM chips
AM9016EDC (AMD) chips are the same as 4116 chips.
IMS2600P-12 (Inmos) chips work in any upper RAM position (IC15-22)
41256 chips work in place of 4164 upper RAM chips
V53C256P80L chips work in any upper RAM position (IC15-22)
MN41257-12 chips work in any upper RAM position (IC15-22)

NOTE: At least one person has experienced problems substituting TR4 ZTX650 with a BC487. Transistor worked, but became hot during use.

QUOTE: DEATH let me remind you that I was having overheating problems when using the BC487 instead of ZTX650 as a tr4 (in 3 boards). When replaced with the ZTX650 no problems any more.

Thanks to George for that one.

74LS series of chips can be replaced with 74HCT chips

odious wrote: »

ZTX 312 at TR1, TR2, TR3 and TR6 on an issue 3B board.

Thanks to Odious for that info.

Steve(spt) · December 2006

This list here is also handy to know about.

DEATH · December 2006

I'll update the list and re-post. If you could let me know the author of that site, I'll add his name to the list also.

Steve, many thanks mate! :)

EDIT: Thanks for the PM steve.

Winston · December 2006

Presumably, 74HCTxxx will work as a drop-in replacement for 74LSxxx. Not tried it though.

Quazar · December 2006

Winston wrote:

Presumably, 74HCTxxx will work as a drop-in replacement for 74LSxxx. Not tried it though.

Yes, you should have no problems there. HCT is fine for mixing with TTL and CMOS 74 families.

The LS family is slowly dieing off, HCT is now the standard, with the faster ACT becoming more mainstream for 5v.

piters · December 2006

Winston wrote:

Presumably, 74HCTxxx will work as a drop-in replacement for 74LSxxx. Not tried it though.

74HCT... is good. Even 74HC... will work fine (for case when no other at hand).

I think that latest series of Speccies had HCT chips.

Some more advanced replacements:
8x 4132 and 2x 74LS157 and 74LS00 and 74LS32 can be replaced with one 32KB static RAM chip and 74LS00.

8x 4116 may be replaced with 2x 4464 (4-bit wide chips). Then no need for +12 and -5V for RAM.

Last but not least: RF modulator may be replaced with composite video out :D

DEATH · December 2006

piters wrote:

74HCT... is good. Even 74HC... will work fine (for case when no other at hand).

I think that latest series of Speccies had HCT chips.

Some more advanced replacements:
8x 4132 and 2x 74LS157 and 74LS00 and 74LS32 can be replaced with one 32KB static RAM chip and 74LS00.

8x 4116 may be replaced with 2x 4464 (4-bit wide chips). Then no need for +12 and -5V for RAM.

Last but not least: RF modulator may be replaced with composite video out :D

As you say, these are advanced, but I wouldn't say that are replacements. They are more like modifications. If you can show exactly how to do the modifications though, I would be more than happy to see it.

DEATH · December 2006

Winston wrote:

Presumably, 74HCTxxx will work as a drop-in replacement for 74LSxxx. Not tried it though.

I have, and yes, they work fine.

piters · December 2006

DEATH wrote:

As you say, these are advanced, but I wouldn't say that are replacements. They are more like modifications. If you can show exactly how to do the modifications though, I would be more than happy to see it.

It is replacement in meaning that is functionally equivalent. And is some kind of modification of course.
I think that it can be interesting, because of usage of newer components, perhaps easier to find, and less power consumption.
I will put some instructions/schematics on my site about 2 mentioned RAM rep/mod...

DEATH · December 2006

piters wrote:

I will put some instructions/schematics on my site about 2 mentioned RAM rep/mod...

That would be brilliant, thanks!

DEATH · December 2006

Added the AMD AM9016EDC RAM chip.

chammyman · December 2006

good stuff, despite me looking through the 3 pages in this hardware section I missed this post.

I can now get the transistors needed.

DEATH · December 2006

You only had to ask dude :)

Seriously, yeah, I've been thinking about getting a list of equivalents together for a while now. Sometimes you can get lucky and get the "proper" bits from Ebay, but more often than not, you have to either scrap a Spectrum, or buy a broken one from Ebay and trash that rather than fixing it.

For now, everything except the ULA, the LM1889 and modulator can be either fixed or replaced. It won't be too long and we'll have real problems getting hold of stuff like RAM chips, Z80s etc. So, knowing what you can use in place of (say) a ZTX450 has to be useful. Hopefully, some of the guys from Eastern Europe will join in with equivalents data of their own, so I'm hoping this list will grow and grow. There are only a few people still repairing Spectrums though, so the list won't be too useful - but every little helps - and no, it's not Tesco's :lol:

Tom-Cat · December 2006

Death: One hellua list ! I really appretiate it and I am sure many others will too. I have quite a few spectrums in need of repairs and this will surely help (for when I get some time and actually repair them). I must also thank Spirantho for sending me a few ZTX's ... they helped repair one of the speccies.
One can only wish that there was a cheap'n'easy membrane replacement.

TC

DEATH · December 2006

hi TC - good to hear from you mate.

Membranes - yeah, if I could work a way of making them myself, I would. 6 or 7 quid for a 48K rubber key membrane is fair enough, but I will not pay almost 20 quid for a 128K membrane. I don't care how much they cost to make etc, I simply will not pay it. There are alternatives, tactile key switches on a PCB bolted onto the Spectrum case is a workable solution - just need to work out how to make it slim enough to be able to close the sace :)

For membranes, try RWAP or Trade-in-post, Shifnal.

Winston · December 2006

I was thinking - functionally, what does the ULA do? It allows tape load/save and deals with the screen and keyboard. With modern parts and a small LCD panel, you could probably do the equivalent using an LCD and a microcontroller and a bit of logic. You could probably use a Z280 - still made, and you can buy them from RS in a monster 64 pin DIL package - modern static RAM and a modern flash ROM to replace the memory. But I suspect at that point, you probably can't really call something with an LCD, a Z280, modern SRAM/Flash ROM a Spectrum any more even if it works like one :-) All you'd have left of the original machine would be the keyboard!

DEATH · December 2006

Added ZTX750 in place of ZTX213 @ TR5's position.

DEATH · January 2007

Winston wrote: »

I was thinking - functionally, what does the ULA do? It allows tape load/save and deals with the screen and keyboard. With modern parts and a small LCD panel, you could probably do the equivalent using an LCD and a microcontroller and a bit of logic. You could probably use a Z280 - still made, and you can buy them from RS in a monster 64 pin DIL package - modern static RAM and a modern flash ROM to replace the memory. But I suspect at that point, you probably can't really call something with an LCD, a Z280, modern SRAM/Flash ROM a Spectrum any more even if it works like one :-) All you'd have left of the original machine would be the keyboard!

Many games wouldn't work on that processor - the illegal opcodes aren't supported I think. I will stand to be corrected tho.......

List has been updated again - info on TR1/TR2 ZTX313

Winston · January 2007

On the Z80, someone (perhaps here?) pointed me to a Farnell page - you can still buy brand new bog standard 40 pin DIP packaged Z80s (albeit the CMOS rather than NMOS version). It's even ROHS compliant.

DEATH · January 2007

That's very interesting - I'm very sure the CMOS version works fine in a Speccy. Nice work!

odious · May 2007

Hi,

I have a issue 3B that has:

MPS 2369 in TR1, TR2, TR3 and TR6.

By the looks of the solders, they weren't replaced. They were placed during factory production.

Hope that helps.

DEATH · May 2007

odious wrote: »

Hi,

I have a issue 3B that has:

MPS 2369 in TR1, TR2, TR3 and TR6.

By the looks of the solders, they weren't replaced. They were placed during factory production.

Hope that helps.

Updated, thanks!

odious · May 2007

Two more:

BC 549B in TR9 and TR8 on a issue 6A

Cheers

DEATH · May 2007

odious wrote: »

Two more:

BC 549B in TR9 and TR8 on a issue 6B

Cheers

I've never seen an issue 6b board! Cheers, updated :)

odious · May 2007

DEATH wrote: »

I've never seen an issue 6b board! Cheers, updated :)

Oops. It's a 6A. Sorry.

Cheers.

DEATH · May 2007

odious wrote: »

Oops. It's a 6A. Sorry.

Cheers.

:) Fixed.

gtsamour · May 2007

DEATH let me remind you that I was having overheating problems when using the BC487 instead of ZTX650 as a tr4 (in 3 boards). When replaced with the ZTX650 no problems any more.

DEATH · May 2007

Ok George, I've added your text and given you a credit for pointing it out. Thanks :)

odious · May 2007

Hi,

MPS 6727 in Q1 on a TC2048 issue 4b (replacing a ZTX 750)

Cheers.

DEATH · August 2007

Added two more chip types that work in uper RAM position (IC15 - IC22)

naz2000007 · August 2007

Where is the updated summary of replacement parts?

Atm all I can see is some parts in replies in this post.

Thanks

Component Equivalents/substitutions

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