- Bad chip resistors? - 2 Updates
- Need a transistor for a '70s Zinger Color Organ - 1 Update
| Phil Allison <pallison49@gmail.com>: Jun 28 03:15AM -0700 Hi, recently came across an SMD board with lots of chip resistors (0805) and similar size ceramic caps. There was mild surface corrosion on the ends of each resistor - enough to prevent a DMM from reading the value until cleaned with a "fibre pen". For the puzzled, it's an essential servicing tool. https://www.ebay.com.au/itm/Fibreglass-Pen-Fibre-Pen-Pencil-Abrasive-Cleaning-With-5-Fibre-Refills-/310094191492 The item itself looked new, but was in fact 9 years old. Eventually I found 3 open resistors, all with values like 1Mohm. Googling tells me this is a known hazard not shared with through hole parts - has to do with the use of silver plating on top surface of the resistor being subject to sulphiding and similar air borne contaminants. Any insights? .... Phil |
| legg <legg@nospam.magma.ca>: Jun 28 09:11AM -0400 On Sun, 28 Jun 2020 03:15:16 -0700 (PDT), Phil Allison >Googling tells me this is a known hazard not shared with through hole parts - has to do with the use of silver plating on top surface of the resistor being subject to sulphiding and similar air borne contaminants. >Any insights? >.... Phil As formation of sulphides is a surface phenomenon, I doubt it plays a role in properly reflow-soldered junctions. Mechanical stress can. Needle-pointed probes are quicker, though possibly painfull when left lying around. Detachable ones make sense, if they don't get lost. RL |
| legg <legg@nospam.magma.ca>: Jun 28 01:33AM -0400 >Hello. The Zinger is a six light alternating and flashing unit. It could run either on with varied speeds or connected to a speaker wire or radio output to pulse with the music. I am trying to fix this bedraggled old thing ... I know, glutton for punishment. Anyhow, the transistor (which is quite toasted) is a Toshiba FIR3D41. I can find no info online about this part or what the replacement might be. Based on what it is supposed to do, are there any suggestions for a replacement? It is 120v and the model number is 528. Thanks for any info ! Toshiba made an SF1R3D41 - Note '1' , not 'I'. 200V 2A SCR in TO202AB package ('R') - anode center pin It has a normal (not sensitive) gate ~ 10mA. "D" is the voltage. (B=100V, G=400V) This from a xref published in Singapore in 1990 - the only reference I could find, and I've got the Toshiba catalog (where there's no mention of it). Light 'chasers' were popular in the 70's, along with Disco . . . You could use a Teccor S2006F1 through S6006F1 (200V -600V) to replace it. Only the physical package is ~ uncommon. Most TO220 types would function, if they could fit. RL |
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