Leaderboard

BC183L ......602133 ISS. B on the underside 2N3904.......602133 ISS. D on the underside

BC183L pinout E C B 2N3904 pinout E B C the 4.7k resistor always goes to the base of the transistor they most likely changed because of supply problems with the BC183L at the time they was being produced, they did use BC183L on the later cards with the eprom sockets on so perhaps they had sorted out the supply troubles!! quite possibly BC183L were cheaper than sticking with 2N3904, well that's my 2p worth!

You will see

Any thoughts on this? Magik recons it’s a early vision due to its colour, thought I’d post it on here.

ram is usually good on these, I don't think I have seen one where the ram was faulty, the main cause of troubles can be the zn404, they are old, obsolete (very expensive) and go temperature sensitive these days causing a fair few troubles.

these 2 transistors Q1/Q2 are quite important! they isolate the ram during power up/ power down so the ram does not get corrupted! if you remove them the card will not boot up! if the wrong transistors are put in the card WILL boot but it will not be long before the ram corrupts as the ram protection will be non existent!

I’ve got the 1996 one mate but looks the same as 1994 I think

I need a yellow one now 😎

My boards wll never be on ebay,maybe machines without boards.Far to precious as i will always have mb1a

Interestingly I have searched through the boards I have here and I have found one with the 2N3904 on it as well! looking closely these are NOT interchangeable to replace the BC183L devices, this is the reason.... If the 4.7k resistors (which are just above the transistors R4 and R6) go to the END pin on the transistors then BC183L are used , these are the ones with the transistor put in reversed to the silkscreen, on the back in the copper markings are marked 602133 ISS. B When the 4.7K resistors go to the MIDDLE pin of the transistors these are the 2N3904 transistors put in the same way of the silkscreen! in the copper markings on the back are marked 602133 ISS. D there is NO WAY you can substitute one for the other by just turning the transistor round 180 deg, so if they are fitted with one type it is best to replace with the same type!