Tascam 388 power supply question

sweetbeats

Reel deep thoughts...
No mate, it was in J.harv's list. I just noticed one device I clicked on a random was a Darlington. Don't mind me, nit picky old duffer!

Dave.
Oh okay. Yeah I saw those too…the NPN list is a total mish-mosh of all types.
 

sweetbeats

Reel deep thoughts...
I don’t know what all is different besides the additional transistors. What those do is provide some regulation for one of the non-audio power rails. If I had to wager a guess I’d say Teac made that change because it was determined long-term the unregulated power may have put components at risk for earlier failure than desired…something like that…so by adding some regulation it may extend the life of the components powered by that power rail. So that’s my guess…not necessarily more reliable as far as the PSU assembly goes, but may help the device, the 388, to be more reliable. This doesn’t mean units were dropping like flies, but more likely it was something considered during the design stage and the bean-counters required that element to be “value engineered” out to save some cost, and during the product life cycle it was determined to be worthwhile to add it in.
 

j.harv

@#$%
Just came across this video. A guy refurbishing a 388. He starts off his video with the power supply. It's the same version 2 one that Im going to recap. Im also going to replace the transistors by the heat sink. Now, he is saying that the pins on the transistors are pinned out differently on the board, which is kind of beyond my knowledge. Looks like he is repositioning the legs of the transistors. This is within the first 3 minutes of the video.
Anyone maybe want to chime in about this? My transistors are on the way and I don't want to put them in wrong.

 

sweetbeats

Reel deep thoughts...
What he’s saying is he’s purchasing a part with a different pinout configuration than one of the original parts, because he doesn’t want to wait for one with the matching pinout to be in stock. If you get any of the bigger power transistors I linked, same pinout. If you get the C1815 part I linked, same part as originally installed, same pinout. Does that make sense? To be double sure, if you want, post a link to the parts you’re looking to purchase or purchased and I can verify whether or not they are direct drop-in replacements.
 

j.harv

@#$%
What he’s saying is he’s purchasing a part with a different pinout configuration than one of the original parts, because he doesn’t want to wait for one with the matching pinout to be in stock. If you get any of the bigger power transistors I linked, same pinout. If you get the C1815 part I linked, same part as originally installed, same pinout. Does that make sense? To be double sure, if you want, post a link to the parts you’re looking to purchase or purchased and I can verify whether or not they are direct drop-in replacements.
Okay, thanks. Upon watching again, I heard the part about him waiting for a replacement. I’ll try and pay attention next time. 😁
The parts that I got were the first ones you linked for each transistor. I guess all I need now is some heat sink compound. That’s readily available localy.
 

skywaveTDR

Active member
If a transistor like 2SC1815 gets warm or hot then I would simply put in a larger transistor like a KSD1616A which is good for 1 amp and .75Watt with 60 V breakdown plus the pin out would match being ECB. I am not one for fooling around as my repairs are expected to last by me. Mouser has the KSD1616 and they are made by fairchild.
 

skywaveTDR

Active member
I have had to transpose leads on occasion but that is not my first choice as a better part that is specified above can be put in with correct lead positions. When I transpose leads I put a PVC jacket tube on two of them because you never know who will get into the unit and bend something down and then blame you for putting in the wrong part. The glue on that board should be scraped off with a razor blade as it looks like that acid stuff that eats component leads and is at times conductive. People that work on this equipment rather than make mistakes due to transistors should learn how to use the Diode test on a Fluke like meter to ID leads- It is very easy to do and inside of a minute I can tell you where and what they are. Data sheets help those that do not know how to do this but if you work on electronics it is time to learn.
 

skywaveTDR

Active member
Okay, thanks. Upon watching again, I heard the part about him waiting for a replacement. I’ll try and pay attention next time. 😁
The parts that I got were the first ones you linked for each transistor. I guess all I need now is some heat sink compound. That’s readily available localy.
Heat sink silicon or white Zinc Oxide past can be purchased but to be honest it is old school and so in my service business I went on E bay and bought a bunch of TO-220 sheet called Silpads that do not need the silicon or zinc paste. I have all that stuff here but Silpads just do a cleaner job. I think I bough like 200 at the time. He does not say what transistor he is using that he has to twist around but I would just as well put in the KSD1616 and be done with it. One should also learn how to read and understand the basic transistor specs and in doing so will make their entire career easier down the line. I learned mine in Engineering college but you need not go that far. Also there is a web site called Alldatasheet that gives good specs and data sheet and in some links a long list of compatible transistors as well at the bottom. Here is the 2SC1815 transistor- https://www.alldatasheet.com/datasheet-pdf/pdf/30083/TOSHIBA/2SC1815.html
 
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