Search found 448 matches

by gozzo
Fri May 12, 2017 4:43 pm
Forum: Hardware
Topic: Proper voltage for ZX81 AC adapter
Replies: 20
Views: 3147

Re: Proper voltage for ZX81 AC adapter

..thin the varnish down a bit to help it seep in all the spaces..... you can get proper 'transformer varnish', but i've used normal wood varnish before, maybe not advisable really as i think the proper stuff is less flammable in case of gross overheating....but the thermal fuse should pop long befor...
by gozzo
Fri May 12, 2017 1:21 pm
Forum: Hardware
Topic: Proper voltage for ZX81 AC adapter
Replies: 20
Views: 3147

Re: Proper voltage for ZX81 AC adapter

many 50/60hz transformer based psus 'buzz' , especially if the laminations are a bit loose, normal,. but, if it gets warm/hot even with no load, could have shorted turns ... loud buzz on load could indicate problem with one or more of the diodes gone open circuit, making it half wave instead of full...
by gozzo
Thu May 11, 2017 9:06 pm
Forum: Hardware
Topic: Proper voltage for ZX81 AC adapter
Replies: 20
Views: 3147

Re: Proper voltage for ZX81 AC adapter

and..beware,..i have a UK1200 psu with the same smaller transformer as the UK700..and it appears to have got VERY hot as the pcb is blackened, although still works, gets fairly warm even with no load,..so...there may be others out there....
by gozzo
Thu May 11, 2017 9:04 pm
Forum: Hardware
Topic: Proper voltage for ZX81 AC adapter
Replies: 20
Views: 3147

Re: Proper voltage for ZX81 AC adapter

as for replacing the 7805 with a switchmode thing, this doesnt help with the rampack voltage problem, but will certainly reduce the heat in the computer...or you could try fitting a full width heatsink? sprayed with a thin layer of matt black barbecue paint...??
by gozzo
Thu May 11, 2017 9:02 pm
Forum: Hardware
Topic: Proper voltage for ZX81 AC adapter
Replies: 20
Views: 3147

Re: Proper voltage for ZX81 AC adapter

my zx81 and spectrum psu's always seemed to me as if you could fry eggs on the things...😉 but...using a modern regulated 9v psu on a zx81 could be a problems as some rampacks used the 'higher than 9v' line as a 'near to 12v' for the '12v' for a bank of 4116s, so 9v wont work, but if 11 ish, probably...
by gozzo
Thu May 11, 2017 8:36 pm
Forum: Hardware
Topic: ZX8-CCB installation help
Replies: 22
Views: 2883

Re: ZX8-CCB installation help

even if you want to use your machine 'every day' (through composite) , still no need at all for modulator murder, just tack the ccb board onto the top of the modulator case(it wont be seen), wire it in as usual (disconnect the modulator 5v and input if you wish, but not necessary)... this way the mo...
by gozzo
Thu May 11, 2017 8:33 pm
Forum: Hardware
Topic: ZX8-CCB installation help
Replies: 22
Views: 2883

Re: ZX8-CCB installation help

you dont NEED to remove the modulator board from its case..but if you must...easiest is to remove the thing completely from the main board, remove its bottom cover, and there are a few solder points where the board ground is connected to the case, unsolder them, the 47 ohm to the phono contact, and ...
by gozzo
Wed May 10, 2017 8:11 pm
Forum: Hardware
Topic: ZX8-CCB installation help
Replies: 22
Views: 2883

Re: ZX8-CCB installation help

aarrggh, another modulator butchered, absolutely unnecessary, you can fit the ccb externally or even on top of the modulator case.... :(
by gozzo
Fri Apr 28, 2017 4:45 pm
Forum: Hardware
Topic: Refurbing an issue one zeddy
Replies: 77
Views: 8790

Re: Refurbing an issue one zeddy

why change the regulator? is it faulty? if not, leave the original in... and as for capacitor polarity..i have come across some that have a + sign within a red arrow :o , but they were quite old, probably some of the first of that style..?!
by gozzo
Sat Apr 22, 2017 10:29 pm
Forum: Hardware
Topic: G007 hires unit - documentation wanted
Replies: 14
Views: 1430

Re: G007 hires unit - documentation wanted

..it does..... i'm not sure who originated this design but looks identical (and probably is) to the Maplin zx81 hires graphics board...maybe it originated from there?! there is(was) the full article on the net a while back....