Lodestar 8103AD schematic required - Page 1
Forum section: electronics / repair

author: Pete F
author_rank: Regular Contributor
timestamp: July 09, 2018, 09:20:47 am
content: Can anyone assist me with a schematic for the above power supply? The issue is the the switching between series/parallel/independent. Initially all 3 lights were illuminated and I replaced the 4017 IC that was involved in that function. That has left me now with only 1 light (saying series) but still with an inability to switch.Working through the circuit I'm left to wonder if the 4017 was in fact the correct IC, or of somebody has been here before me and had a bit of a go at it? The ICs are in sockets, so it's not impossible for that to have happened, but to be quite honest I'm just generally scratching my head. It seems the outputs are pins 3, 11, and 14, with pin 9 the buffered switch input. That doesn't make any sense to me as a 4017.I've had a look through similar counters to see if those pin outs made any sense with any other ICs, but aren't coming up with anything. 4017s are cheap so I've tried replacing it a second time, the initial replacement definitely did something, but it's obviously still not correct now.I've obviously contacted Lodestar to ask for a schematic but aren't exactly holding my breath!

author: coromonadalix
author_rank: Super Contributor
timestamp: July 09, 2018, 10:25:02 am
content: must have some similarities with mastech models and other clones, check the serial / parallel switch, must be some kind of relays / switching logic behind itBut all the models I've seen are with dual switches ...

author: coromonadalix
author_rank: Super Contributor
timestamp: July 09, 2018, 10:31:35 am
content: this thread has some schematics :https://www.eevblog.com/forum/beginners/fixing-my-mastech-hy3005d-3/the 4017 must be used for the leds indicators has you said and or some logic relays controlcan you post insides photos ?

author: Pete F
author_rank: Regular Contributor
timestamp: July 09, 2018, 10:38:34 am
content: As I said, the logic is around what is (apparently a 4017). It is the logic circuit that isn't making sense, as described above. It would presumably be a standard counter circuit (as a 4017 would be used for), with a momentary action switch clocking the counter. However the pin outs aren't making sense for a 4017. A lot of other power supplies (including some dual supplies in the Lodestar range use 2 mechanical switches, however this one is different in just using the one momentary action and basic logic.

author: Pete F
author_rank: Regular Contributor
timestamp: July 09, 2018, 11:21:44 am
content: I'm increasingly convinced the 4017 that is fitted is not the correct IC. The switch logic goes in to pin 9, which is actually an output on a 4017. Other pinouts are incorrect in fact. It makes me wonder if somebody looked up what the original counter did, and just jammed this in there?It looks like the outputs that are used (at least as far as I've worked out) are pins 2, 3, 4, 11, 12, 13, 14, 15, pin 9 is the buffered switch input so probably clock, pin 1 is held at VDD so enable (?)Weegee board operators as to what should be there would be most welcome

author: Pete F
author_rank: Regular Contributor
timestamp: July 10, 2018, 11:28:10 am
content: If anyone has a Lodestar 2 or 3 channel power supply with the electronic switching and could identify the ICs used that would be great. It would only mean removing the top cover and checking what the 3 ICs say on them, the logic board is easily seen from the top, so a 5 minute job to help out a brotha

author: Pete F
author_rank: Regular Contributor
timestamp: July 26, 2018, 12:01:18 pm
content: For what it's worth I believe I was correct in believing a CD4017 had been incorrectly substituted for a 40175. A CD40175 has been installed however the circuit still isn't workingThe odd thing is it's a relatively simple circuit in the grand scheme of things, and buffered to the outside world via drive transistors (which check ok). The logic should be purely binary (ie either fully on or fully off). Everything seems to be ok, yet I'm getting some odd logic voltages at a few points.Substituting the CD40175, CD4093, and CD4049 a number of times suggests that they are not faulty, having said that, the supplier of the 4093/4049 provided them with absolutely zero ESD protection (ie stored in plain plastic drawers and sold in a standard plastic retail bag), so it's plausible they're dud, but seems unlikely to have a series with the same symptoms. In frustration I pulled each of the ICs from the circuit and found pulling the 40175 removed most of the "odd" voltages, however that tube should definitely be ok, as they were from a good source.I've emailed the manufacturer AGAIN asking for information, but don't expect any joy there, so I've hit a bit of a brick wall here. All a bit frustrating.