TTi PL303QMD Power Supply, Fan noise? - Page 1
Forum section: electronics / testgear

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 06, 2015, 11:31:31 am
content: Hallo, hope to get some feedback, because I didn’t get any from TTi……I want to buy a new power supply, and I am looking at the PL303QMD ("New PL" series).I like silence in my lab while doing design work, and tend to switch noisy instruments off the moment I don’t need them.But the Power Supply is always on… It’s one of the things I appreciate in my (older) TTi power supplies, they are silent!So, looking at the new PL303QMD, I like it’s features and compactness, but the flipside of that compactness appears to be smaller heat sinks, in combination with a fan.TTi says in it’s literature: "Intelligent variable-speed low noise fan assists convection"But I don’t know what to expect in terms of fan noise in real life / normal daily use….So, to be able to make up my mind, some questions about the fan in the new PL303QMD power supply:Is the fan always on (running slowly), or only at higher output levels of the power supply? (and if so, approximately at what output level is the fan kicking in)Please expand on what to expect (in noise levels) from this “Intelligent variable-speed low noise fan”?To give an idea of my situation: Mostly i will just draw approx. 100-200mA from the Supply, used as dual +- 12-18V Supply. If it is (really) silent at those output levels, I will be happy.Reason to buy this Power supply is that I am looking for a low noise, dual rail power supply to prototype audio (OpAmp) circuits.I found that real dual rail supplies, where both outputs are switched on/off with a single button are thin on the ground these Days.If you have an idea for an alternative, I am very open to suggestions!Interested in other user experiences too....Thanks in advance, Gertjan.

author: wraper
author_rank: Unknown
timestamp: May 06, 2015, 11:57:32 am
content: This is the most used PSU of what I have (I also have Agilent E3611A, 2x 6612C). The huge advantage that you can set it really fast, no need to waste an unnecessary few seconds. Fans do spin all the time but unless you attach significant load, you won't hear them at all.

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 06, 2015, 02:30:10 pm
content: Wraper, thanks for your feedback!I know that fan noise is a very subjective issue.When I am designing & prototyping it is really silent in my room.Do you still think I won't hear the power supply sitting one meter away?Off coarse it is a different situation when there is already a PC on, or the radio etc. etc......Thanks, Gertjan.

author: wraper
author_rank: Unknown
timestamp: May 06, 2015, 02:36:36 pm
content: Probably you'll hear them in completely silent room when sticking your ear 10 cm away from the PSU.

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 12, 2015, 07:50:25 pm
content: After some thoughts I have bought a TTi EL 302RD.Slightly less good specifications, but NO fans..... (at about half the price of a PL303QMD)Most important consideration was that in my experience silent fans are getting less silent over time...I must say I am a bit disappointed that the look and feel of the EL 302RD is a bit flimsy.Knobs and binding posts are wobbly.I am wondering if the more expensive PL series is made more solid....Regards, Gertjan.

author: wraper
author_rank: Unknown
timestamp: May 12, 2015, 07:57:07 pm
content: it lacks all the bells and whistles of the PL303QMD. Again, you would not know there are fans unless run it at full power for prolonged time.

author: pascal_sweden
author_rank: Super Contributor
timestamp: May 12, 2015, 08:44:01 pm
content: Thurlby Thandar Instruments (TTi) is good quality in general, but relatively expensive. But what do you expect, they are a UK based company.I still believe it should be possible to score a Chinese power supply with pretty decent reliability for a much lower price. It's a matter of doing a bit of research, and be optimistic in the search process.Some people will say upfront that Chinese devices are useless, but I believe that this is a negative generalization as a whole for people who don't like to do some homework in the actual investigation of finding a good, but affordable power supply.Chinese manufacturers keep on improving, and impressing, believe meBTW: I am not sure that TTi uses Nippon capacitors. Has anybody actually verified that you get decent caps at all, for the money that you put on the table?Maybe Thurlby Thandar uses caps that are as cheap as the ones in the Chinese power supplies.Thurlby Troubly capacitors which are not Thandar-dized because of low quality

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 13, 2015, 08:33:47 am
content: @ WraperI must confess I am disappointed with the build quality of the EL 302RD. It is really cheap, almost Chinese.The potmeters have soft plastic shafts, so the knobs are wobbly, and scrape against the front panel.The electronics are really basic, one opamp and a few transistors per supply. Looks like the complexity of an average DIY project.(Although it does have the nice feature that it shows the current limit value on the current meter when the supply is switched off)All screws are self-tapping etc.I am considering asking my supplier if they will exchange it for an PL303QMDDo you think the build quality of the PL303QMD is better?I really like the possibility of the PL303QMD to switch both channels together on/off (for dual rail purposes)Other extras like the V-span etc. are less interesting for me.But I really appreciate well built tools (and quit equipment off coarse)And don't mind to spend more money to get better tools.I hope you can give me some extra info on PL303QMD build quality to help me in my decision.....(And wish there was a brick and mortar store, being able to see (and hear...) these supplies side by side would make choosing very easy....)Thanks & regards, Gertjan.

author: wraper
author_rank: Unknown
timestamp: May 13, 2015, 09:20:10 am
content: In PL303QMD potentiometer shafts are plastic too. Though I didn't notice that unless tried to bend them right now. They do not scratch front panel. There is also advantage of dual range current set and meter.Quote from: Gertjan on May 13, 2015, 08:33:47 amBut what did you expect from analog power supply. Post the pictures.

author: wraper
author_rank: Unknown
timestamp: May 13, 2015, 09:40:10 am
content: BTW there is TCA785 phase control IC. Maybe it has something to do with being able to reduce dissipated power.

author: pascal_sweden
author_rank: Super Contributor
timestamp: May 13, 2015, 09:44:01 am
content: Can you verify from which brand the caps are? Maybe even take a close up photo from some caps.

author: wraper
author_rank: Unknown
timestamp: May 13, 2015, 09:46:19 am
content: Quote from: Gertjan on May 13, 2015, 08:33:47 amYou can also switch them in parallel, therefore you have 6A @ 30V when you need it.

author: wraper
author_rank: Unknown
timestamp: May 13, 2015, 09:55:25 am
content: Quote from: pascal_sweden on May 13, 2015, 09:44:01 amThe big cap is Samwha. Other through hole are Elna, Rubycon and Jamicon. Cannot say anything about SMT ones.

author: pascal_sweden
author_rank: Super Contributor
timestamp: May 13, 2015, 09:58:18 am
content: Good to hear that not all caps are from a cheap Wan Hung Low brandI know about Rubycon and Jamicon. But what about the two others?

author: wraper
author_rank: Unknown
timestamp: May 13, 2015, 10:18:24 am
content: Elna are top grade japanese capacitors. Samwha - decent enough Korean brand.

author: pascal_sweden
author_rank: Super Contributor
timestamp: May 13, 2015, 10:29:59 am
content: It made me think about that Korean monitor manufacturer Sampo.When I saw that brand, I was always thinking about Shampoo

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 13, 2015, 11:42:02 am
content: Thanks Wraper for the Photo's!!You convinced me.I arranged with my supplier to exchange the EL 302RD for a PL303QMD.So I didn't want to open it up again for Photo's, but I can tell you there was a lot more empty space in the EL302RD.Only one transformer, one PCB on the bottom of the case with the basic power supplies, and a PCB behind the front panel for the meters.For Pascal: the elco's were all Jamicon. But really, I don't think this is very important in a linear power supply.....I will report about how I like the PL303QMD when I get it....regards, Gertjan.

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 17, 2015, 05:19:19 pm
content: Well, my PL303QMD arrived……On the plus side, it is a much nicer supply than the EL302RD.Build quality is better too…. Actually it is interesting, that while the used materials are more or less the same, the look and feel is very different.The EL302RD looked cheap and felt flimsy. The PL303QMD looks much better, and feels more solid too.Key differences: the legends on the EL302RD front panel is just embossed, in the same color as the panel (white on white), while the PL303QMD has black printed legends.Both have pots with plastic shafts, but those of the EL302RD are softer, and the knobs wobble & scrape against the front panel.The EL302RD meters are having bigger digits, so all digits are closer together (making “one long digit bar”) which makes the meters harder to read.The PL303QMD is easier (less fiddly )to adjust, and the meters are more stable than those of the EL302RDOn the negative side……The fans are noisy (my opinion…) and the transformers make noise because of the phase control pre-regulation.This is not helped by the fact that the supply is standing on a shelf, on eye-level above by bench, about one feet from my ears.Also it doesn’t help that the fans are bolted to the sheet-steel bottom, and the supply is standing on a wooden shelf, acting as a sound board…….Soo… I went down the (for me familiar….) path of silencing this supply.I replaced the plastic feet with soft rubber feet.The fans are now mounted with soft rubber mounts (these:http://nl.farnell.com/multicomp/mcfmm-1/fan-mount-universal-pk4/dp/1293012)I glued bitumen under the transformers, and on resonating panels of the case. (the kind of bitumen which is used in the car industry to damp panel resonances)These mods made a big difference. The phase control noises are gone, and the noise of the fans is much less. (but not silent….)Overall I am happy now with this supply.It is a very nice Power Supply, with all the features I need, easy to set up, and with easy readable, very accurate meters.To be clear about the noise: This is my perception. I like to design my (audio)projects in a silent room, so I tend to switch gear I don’t need off. Also because you sometimes want to listen (closely!) how your prototype is sounding.As soon as I switch on my PC, digital scope, or other test gear with a fan I can’t hear the PL303QMD at all…..Fans in test gear are one of my pet peeves…. I can understand that you need a fan in a power supply dissipating 100W, but in a generator or Bench DVM?Just because a fan is a bit cheaper than a bigger heat sink on the processor?@ Wraper: Thanks for helping me out!Regards, Gertjan.