TTi Thurbly Thandar and age of older models

[off-by-one]

Hello all,

I'm looking for power supplies and TTi seems to be a reputable brand. There are some nice models on the second hand market. But I wasn't able to determine the age of these older models.

There seems to be at least four separate lineups (guessing from older to newer):

1. Gray cover and gray stripe behind the red displays. Bulkier switches. Thurlby logo:


2. Gray cover and LCD dislplays. (with black and white knobs) Thandar logo


3. Gray cover and top part on face plate and red displays. TTi logo


4. Current lineup with mostly white and red displays. TTi logo


Maybe there is even more variation and regional differences?
Anyone know roughly how old the different lineups are?

Are there any significant design differences between the different age models?

[G0HZU]

I'm not that much of an expert on these PSUs but I have been using all variants (as they appeared)across about 25 years.

The one to be most wary of is known as the mark 1.

I have two of these here and the internal build quality is awful. I got both of them as freebies from work when they had developed faults and were headed for the refuse skip about 20 years ago.

The mark 1 dates back to the 1980s and looks similar to your first photo. However, your photo may not be a mark 1 as it looks slightly more modern than my units.

Apart from awful build quality, the mark 1 uses a long obsolete (and not very reliable) display chip.
They are well know for having intermittent displays and wandering current limit issues and also missing LED display segments as well as dead display chips as above.

But on the plus side, they are very nice to use once working and the display is very bright and clear.

[G0HZU]

Just to add, I also have examples of the second and third variants in your photos here at home.

These are vastly improved in terms of internal build quality and are very reliable.

However, I don't like the TS3022S version much because of the very gloomy LCD display. I have two of them here and I wish I'd bought more versions with the LED display instead.

I also have one of the newer TTi PL320s (marked as supplied by RS) with the facelifted LED display (as per your third image) that has a formal cal sticker from 'RS service point' dated June 2001. I would guess that this sticker was fitted when new.

[G0HZU]

I just reread your first post and I think your first image is not a mk1 as it has a grey outer case.

The original mk1 units usually have a brown outer case and both of mine are like this. There may be some mk2s with brown cases though.

The mk1 uses a lashup of direct point to point wiring between PCBs instead of connectors and these are usually soldered badly. They are horrible to work on because you can't dismantle it easily because all the boards are tied together with soldered wires. There are also cheap screw terminals used for a lot of connections from the transformer and these work loose over time. They also suffer from dried out electrolytic caps in the display board and the quality of the wire to wire soldering on the display board is best described as being done very late at night by a very tired novice using a crappy soldering iron and recycled solder.

The later TTi PSU models are completely different. They have decent build quality all round and use a board to board connector system that permits easy dismantling and faultfinding and the quality of the soldering on the PCBs is much better than the mk1.

[off-by-one]

Great info. Thank you.

Now that you say, I've seen some brown units as well. Better to skip those then.

Also good to know about the LCDs. They look pretty good in the pictures, but I guess you can't beat self illuminating displays.

[G0HZU]

Here's an old image of my two mk1s.

Also an image of the insides of one the last time I repaired it. You can see the horrible interconnection system it uses.

They are even worse to work on once you begin to dismantle them to try and faultfind because the stiff wires used between boards will not want to flex much and the PSU will fight you...

But the reward is that they are very good to use once you get them working reliably

[McBryce]

"I'm not that much of an expert on these PSUs"... and then goes on to show that he IS an expert in these supplies

Great info GOHZU and full points for modesty.

McBryce.

[G0HZU]

Also good to know about the LCDs. They look pretty good in the pictures, but I guess you can't beat self illuminating displays.

As I sit here and look across my workroom I have an LCD TTi PSU on my bench and also the facelifted 2001? PL154 model with the LED display sat on top of it on a bench.

I'm at about a 45 degree angle and maybe 2.5 metres away from the PSUs but I can clearly and effortlessly read the display numbers for voltage and current on the LED PSU and could probably do this at double/triple the distance. But I can't easily tell if the LCD PSU below it is switched on let alone read the display digits.

The LCD display looks nice if you have it at eye level and there is good lighting. But once you are at an angle and the lighting is less than ideal it becomes much harder to read the display. So if you plan to only use this PSU when sat close to it you may not have an issue. But if you work in a large room and want to keep a casual eye on this PSU to monitor current etc then it is no good because it is so hard to read at an angle or even when you just stand up in front of it or in less than ideal lighting. The LED display is so much better here.

I'm not really that much of an expert on them because some people have repaired dozens of these PSUs and know them very well. I've maybe cleared half a dozen very common faults on my mk1s over the last 20 years.

[G0HZU]

For completeness here is an image of the insides of the newer (2001?) PL320 I have here.

You can see the vast improvement in terms of inner build quality. See also the connection system that also allows easy dismantling.

[G0HZU]

I also found another scary image of the insides of one of my 'brown case' mk1 PL320s that was built maybe 25 years ago.

They even used cheap screw terminal connectors for the 230V AC wiring. Also check out the poor soldering of the main PCB and the bird's nest wiring with soldered wire connections between PCBs (to save money?)

[lowimpedance]

 I have a 'brown' cased PL320QMD which must be a mk2 as it uses an A/D and PIC micro to drive the displays. Similar internal construction to GOHZU later model pic.
Still had a few questionable construction choices but nothing that could not be gotten around if motivated.

My unit was found discarded due to one channel being toasted from the series pass transistors to the AD and PIC, I was able to read the firmware from the good channel and thus rebuild the dead one. After a few tweek's for the tracking I quite like using it and its been a good number of years since and its never missed a beat.
 So for the 'right price' don't totally discount the older ones from your choices.

PL320QMD Service Manual attached for reference.

[KJDS]

I also found another scary image of the insides of one of my 'brown case' mk1 PL320s that was built maybe 25 years ago.

They even used cheap screw terminal connectors for the 230V AC wiring. Also check out the poor soldering of the main PCB and the bird's nest wiring with soldered wire connections between PCBs (to save money?)

I suspect that wiring harness approach was more because they didn't know any better. It was common on a lot of stuff designed back in the 70's and carried on into the 80's and early 90's. The mk1 are horrible to work on, whereas the mk11 are so much easier.

[nidlaX]

Aren't some of the recent TTi programmable supplies Chinese (Tenma) rebadges?

[PTR_1275]

I've got 2 pl330's here in the workshop. One old, one new (newer). Only difference between them is the newer version is using mostly smd chips on the front panel. All of the pots etc... Are in the same location. The older one has date codes inside from late 95 / early 96. Firmware version is pic pl v2 1.00

If anyone has a PDF of the service manual they could send through that would be great. I contacted tti before Christmas and haven't heard anything. The newer one could do with a bit of a tweak to the current and voltage displays. The older one is in pieces, current isn't reading and as a result won't current limit (if anyone has some pointers they would be appreciated)

Cheers
-Chris

[Mark Hennessy]

Telling a Mk1 from a Mk2 is simple:

Look at the "damping" switch. In the Mk1, it's a toggle switch. In the Mk2, it's a small push-button switch.