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Electronics => Repair => Topic started by: uwezi on September 09, 2016, 06:58:50 am

Title: LakeShore 330 temperature controller
Post by: uwezi on September 09, 2016, 06:58:50 am
Does anyone here have a schematic diagram over a vintage LakeShore 330 temperature controller, or could otherwise tell me what component Q6 used to be?

I "fixed" the controller last week, where an OPA541 power opamp had blown out its magic smoke and it worked again for a couple of days, just to then burn up a TO-220 device on the same heatsink. Of the type number only the last two digits remain legible: ...15

Since its right leg was connected to the positive rail of the power opamp and since all other TO-220 parts inside are voltage regulators (plenty of them) I falsely assumed it must have been a 7815 - in the hindsight quite clear that it could not have been... :palm: - but I was proven wrong by a small explosion...  :-BROKE
Title: Re: LakeShore 330 temperature controller
Post by: tautech on September 10, 2016, 07:49:39 pm
7915, negative reg, not positive reg 7815 ?

Grab the datasheet for both, check the pinouts and typical application schematics.

Sometimes a pic of both sides of the PCB can help us......
Title: Re: LakeShore 330 temperature controller
Post by: uwezi on September 12, 2016, 11:00:30 am
Quote from: tautech on September 10, 2016, 07:49:39 pm
7915, negative reg, not positive reg 7815 ?

Sometimes a pic of both sides of the PCB can help us......

I thought of the 7915 as well, but it does not make sense either at this position. Also as I saw later all 78xx and 79xx are labeled as Uxx on the board (as they should), while the burned part was Q6. I suppose it might have been a MOSFET like an "...N15" or "...P15"
Title: Re: LakeShore 330 temperature controller
Post by: uwezi on September 14, 2016, 03:51:36 pm
Let me rephrase my question:

After a more detailed analysis of the traces and connections around the burned Q6:

Is/Was there a power NPN transistor around in the mid-1990s:

I am now quite sure that the transistor was part of a discrete voltage regulator with two zener diodes as references (1N5363 alone and 1N5363+1N5360 in series). The switching between the two ranges was done through a relay which also switched between two taps on the mains transformer.
Title: Re: LakeShore 330 temperature controller
Post by: Kleinstein on September 14, 2016, 04:25:04 pm
The BCE pinout it the normal one for TO220 transistors. So plenty of transistors to choose from.

For the BD series, there are some types with subtypes of -40 / -25 and -15. There might also be 2Nxx15 or 2SCxx15.
Title: Re: LakeShore 330 temperature controller
Post by: little.tesla on June 28, 2022, 06:53:34 pm
Hi,

sorry for resurrecting this thread.

Did maybe somebody in the meantime find a schematic of this device or did dump it's firmware?
Title: Re: LakeShore 330 temperature controller
Post by: khach on June 29, 2022, 07:45:51 pm
Schematic diagramm
Title: Re: LakeShore 330 temperature controller
Post by: zrq on September 13, 2023, 01:45:36 pm
I got hands on a Lakeshore 330 in the exactly same condition. Q6 was cut and removed by the previous owner and the OPA541 exploded. If anyone needs a memory dump, drop a message and maybe I can help.