rethinking this… is there an easy way to create a 300mA load on the 5V chain so that I can test prior to buying one? I have lots of standard 0.25W resistors flying around, how would I chain them correctly?
To get the resistance required to generate 300mA on a 5V supply, you divide 5(V) by 0.3(A) which gives you 16.6Ohm’s. The power required (in Watts) can be obtained by multiplying 5(V) by 0.3(A) which is 1.5W.
If you put equal value resistors in parallel, it half’s the resistance and doubles the power handling capacity so you could put 10 x 160R 0.25W resistors in parallel which would give you 16R which would produce a load of 312mA on a 5V supply. You could probably get away with 5 x 80R but they might get a bit warm
second the notion Re. interest in participating in a bulk order for the noritake alleged drop in. I picked up an IEE VFD that showed up cheap on Ebay, but found that it’s mechanical dimensions were slightly too large for the spacing in the control surface PCB. Haven’t yet gotten to the point in assembly where I could test compatibility, but had pretty much written it off because of the size issue.
this topic also brings up the interesting question, Are the worst case scenarios for power consumption on the various supply rails using all 6581’s, 8580’s etc. known? All the references i’ve seen in the docs simply refer to using the C64 PS or building an externally regulated unit, if one were building one, what should the carrying capacity be on the various rails to account for all possible conditions?
If the SIDs are at the max current, then it’s ~1200mA.
9V supply usage is ~320mA
I would say you would be safe with 2A on the 5V and 0.5A on the 9V/12V. I am building a PSU now and I use a 15VA 7.5V transformer (2A) for the 5V and a 15VA +12V/-12V center tap transformer (0.625A) for the 9V and it works. Right now I have some noise in the audio, but I don’t think it is because the transformers are too small.
I have the feeling that the noritake VFD is not greedy on power, as it is rated the same (275mA) as some LCD backlights. That is a good character trait and makes it really useful as a drop-in lcd replacement :-).
Ok, here is a pic with added load on the 5v chain.
My setup is a standard C64 power brick, 8x8580 - I am playing some notes on all 8 sids for some time now and so far everything looks stable, will leave it on for a little longer, though…
The breadboarded resistors actually only add ca 190mA current consumption on the 5V rail, because my multimeter is a very el-cheapo variant and can´t measure higher currents than 200mA.
That´s why I left the backlit LCD connected… in conclusion, if the VFD does not take more than 200mA more than my used backlit LCD (which is rated for 200mA), it will work.
Of course, using a newly built custom PSU, you are on the safer side, just make sure that you catch no noise from switching PSUs.
Regarding the bulk order - I am not sure, that this is going to happen, as the items are quite pricey and we would need to get 10 people interested in them with cash prepayment for a significant rebate - i would not like to run such a thing for sure, because of the hassles involved.
I will order one noritake VFD soon, as I love the MB-6582 (really!) and will keep you posted regarding the compatibility: dimension-wise, as well as driver-wise. I am quite confident now, that for a 8x 9V SID setup (8580/6582) at least the C64 PSU is good enough for use with this VFD.
Sorry for double posting - just before ordering, I have identified a potential fitting conflict of this VFD, if you look at the vacuum tube and the components on top of the vfd glass case on the right diagram in the datasheet:
so either the vfd has to be mounted ca 7mm deeper, which might be problematic because of the already quite stuffed pactec pt-10 or we have a fitting problem… Argh &§"/$(!
If anyone else is also VFD hungry… the above-mentioned display from Noritake fits quite nicely into the MB6582 (its outer dimensions regarding components on the pcb differ from the schematics in the datasheet). I will update the mb6582 photo tutorial soon with pics and installation guidelines.
The display needs a little bit of driver patching, though. I´ve updated a clcd driver, that works fine for me now, you can find it here:
