Recent Posts

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Power/Renewable Energy/EV's / Re: Aussie Fast Charger Company Tritium Goes Bust

« Last post by quince on Today at 01:18:31 am »

The green pullback is severe whiplash for these overdone companies I think.
Downturn - Tesla is getting trashed too, laid off 10% or 6,000 staff in California and Texas. Let's just blame the economy, not the Cybertruck fiasco, not the CEO, not the silly expensive products etc.
"Andrew Baglino, the senior vice president of powertrain and energy engineering, said on X that he had made the “difficult decision to move on from Tesla after 18 years”. This a  bad omen.

Tesla's stock is up 25% over the past week, though. The layoff was strategically valid.

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Projects, Designs, and Technical Stuff / Re: PC74hct4046ap Replacement

« Last post by dj_holmes on Today at 01:17:34 am »

SN74LV4046A This chip has the same pinout. I think its only SMD where I need the pins but I can try and find an adaptor and solder myself. Its its an improvement its definetly worth a try

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Projects, Designs, and Technical Stuff / Re: PC74hct4046ap Replacement

« Last post by dj_holmes on Today at 01:10:10 am »

Thanks for the replies. There are no issues I'm essentially trying to see if there is a slot in replacement with better parameters or some design tweaks.

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Projects, Designs, and Technical Stuff / Re: PC74hct4046ap Replacement

« Last post by moffy on Today at 01:08:29 am »

Ran across this discussion: https://e2e.ti.com/support/logic-group/logic/f/logic-forum/997347/cd74hc4046a-jittered-free-running-vco-signal
It mentions that for similar timing cap values that the jitter is high. The suggestion was to replace the 74HC4046 with the 74LV4046a part, not sure how that would work in your application you might need to change some values.

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Power/Renewable Energy/EV's / Re: Dual Complementary Rectifier PSU

« Last post by bdunham7 on Today at 01:01:02 am »

It isn't a simple calculation and you would need to know the DC resistance of the transformer secondary, the size and ESR of the filter caps and other stuff to do it mathematically.  Practically, for a FWB you'll see RMS-to-average ratios of 1.5 to 2.  However, since you are drawing your power mainly from the +15V rail, that will be supplied alternatively from each half of the transformer so I think the results might be a bit different.  Using larger filter caps actually makes the RMS-to-average ratio worse (higher) so if you are close to the transformer limits, don't make them any bigger than needed.  In any case, I'm pretty sure your 60VA transformer is sufficent for the task you've specified.

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Microcontrollers / Re: Routines to convert binary to BCD in C code

« Last post by John Coloccia on Today at 01:00:38 am »

Depends on the processor. Some processors fall flat on their face with floating point calculations.

But yes, many cases of poor performance are due to IO bounds, not computation.

Is there an actual problem that's trying to be solved here?

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Projects, Designs, and Technical Stuff / Re: PC74hct4046ap Replacement

« Last post by moffy on Today at 12:58:59 am »

The VCO is in a feedback/PLL loop with PC2out as the comparator (the custom chip must be generating some reference) and R303,R304,R334,C302 as the loop filter. If you have stability issues it is most likely due to the phase comparator and loop filter, unless you have switching noise directly affecting the VCO. Can't comment much further as we don't know what is going on in the custom chip.

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Projects, Designs, and Technical Stuff / Re: Vacuum Fluorescent Display Driver

« Last post by bostonman on Today at 12:45:57 am »

The G lines are equally confusing. This is with a frozen 5MHz (5.0000000000) on the screen.

The data on the analyzer lines that are not labeled weren’t connected. For some reason they are picking up stray signals and showing on the captures.

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Projects, Designs, and Technical Stuff / Designing a volume & power switch for an old McIntosh Preamp

« Last post by neevo on Today at 12:42:02 am »

Hello everyone! I have over the past few years been restoring a beautiful McIntosh C20 Tube Prepamplifier. These date back to the 1950-60's and are a glorious bit of kit. My restoration is now complete and I had to make a few parts along the way as these things are no longer supported by McIntosh for a lot of items (understandably so given the age). I documented the whole build process for anyone who is interested on a popular Audio forum.

My latest project is to build a replacement volume and power switch as these are known to go bad on a few vintage McIntosh machines and are also no longer supported. There are reproduction parts available which I have in my C20 (and its working fine), but they are supposed to be all over the place in terms of quality... so I am looking to make a better version that also has the option of being rebuildable if required and also tunable to dial it in perfectly.

The original C20 volume potentiometer has 4 wafers (audio) and a rotating switch all in the same assembly:



The repeated use of the switch is what seems to kill these pots, plus the balance between all the 4 wafers is not even that good

My design uses 4 stepped attenuators but where I am getting stuck is the switch mechanism and thats where I need some help:





I am keen to get rid of the mechanical switch if possible as I think I can get more control from a low voltage wiper and activate something like a relay or Triac. I could use a microswitch, but I find them a pain to set the trigger point and given the stepped attenuators ativate in 10 degree increments, I really want to activate the switch on the first 1 or 2 steps. So my thoughts were to use a voltage divider network to trigger a triac, all using the 120v line voltage on the original switch:



When I simulated this, it looked like it would work but I am not 100% sure and keen to have some experts help me understand to make sure its effective + SAFE! Ideally I would like to put this all on a PCB on the end of my design which also would need to allow for the 120v and 35w of power the C20 uses. The simulator showed only 740mv and 70 uA on the switch, which in concept seems like it will work. But I cannot be 100% sure I haven't used the simulator wrong or made some basic errors.

Hoping to get some guidance here.

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Power/Renewable Energy/EV's / Re: Dual Complementary Rectifier PSU

« Last post by David Hess on Today at 12:38:37 am »

Lets say i need 1.3A from +15V to common 0V, 50mA from -15V to common 0V, and 150mA symmetrical load on+15V/-15V

Just going by my intuition:

1.30/2+0.05/2+0.15=0.65+0.025+0.075=0.75 Amps

However the power factor for a diode-capacitor filter is only about 0.65, so the actual RMS current will be 0.75/0.65=1.15 amps.  This comes about because the capacitor input is only drawing current in pulses during the peaks of the line cycle.