- Sheesh - 4 Updates
- easy way to calibrate audio frequency generator? - 9 Updates
| "ohg...@gmail.com" <ohger1s@gmail.com>: Mar 01 03:18PM -0800 > Silver sulphide would form on the plating, travel into the device and eat the chip. > Always Jap stuff like Marantz. > ..... Phil Yep. I think Chuck one post up identified the number. |
| Phil Allison <pallison49@gmail.com>: Mar 01 03:23PM -0800 ohg...@gmail.com wrote: =============== > > Silver sulphide would form on the plating, travel into the device and eat the chip. > > Always Jap stuff like Marantz. > Yep. I think Chuck one post up identified the number. ** See: https://www.oneonetwo.com/2013/07/vintage-transistors-2sc458-hitachi.html That looks *horribly " familiar.... .... Phil |
| legg <legg@nospam.magma.ca>: Mar 02 09:10AM -0500 On Sat, 27 Feb 2021 12:27:16 -0800 (PST), "ohg...@gmail.com" >> Then there is this quad unit, outputs good but it had more bad transistors than you could sweep off the floor. get the amp fixed and a channel is cutting out. Bad connection ? Nope, a transistor. Got that fixed and now off to another board that is no doubt full of bad transistors. >> Life is trip, think of the destination. >The only time I really remember transistors being a red flag (other than early Germaniums) were some small Hitachi signal transistors from the 70s-80s - the TO-92 ones with the beveled top. Those things would go leaky or open or intermittent (their choice). It got to the point back then that I just automatically changed them whenever I saw one in anything I worked on. Pretty much eliminated any rechecks. We had an issue with parts in TO98, which was a common package for early GE plastic signal transistors. 2N339x 2n34xx. These were encapsulated off-shore, possibly even a simple rebrand. At the time, there was a suspicion that they weren't normal supply chain product, as the bad parts were purchased through brokers. Although conforming to TO98 outline, they were a filled-epoxy package, vs a molded epoxy. Anything showing up with the filled-epoxy construction was simply dumped at incoming inspection. Rubbish. RL |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Mar 02 06:47AM -0800 On Tuesday, March 2, 2021 at 9:09:12 AM UTC-5, legg wrote: > filled-epoxy construction was simply dumped at incoming > inspection. Rubbish. > RL We've all seen flat out counterfeits. When I used to repair an amplifier with blown outputs, I used to return them along with a copy of my do's and don'ts - things like checking for wayward strands of speaker wires, looking for speaker wires punctured under carpet strips, not doubling up speakers on one terminal block, leaving sufficient ventilation on top of the amplifier, etc. I remember when I had amplifiers coming back with reblown outs, and I blamed the customer. Turns out the semis I was buying were counterfeits, and it wasn't just audio transistors. We ran into this problem with television vertical output ICs, power supply ICs, horiz (line) outputs, STK convergence modules, and even Sony jungle ICs.. I remember going through my parts supply and tossing a good portion of them out and making sure to buy from only reputable suppliers or directly from the OEM. |
| Tim R <timothy42b@aol.com>: Mar 01 09:04AM -0800 Cheap USB microphone, laptop, Audacity? (Audacity is free recording software with lots of extras, does frequency, etc) |
| liz@poppyrecords.invalid.invalid (Liz Tuddenham): Mar 01 07:46PM > scale really. Output is from 200 Hz - 2 Khz on "low" and 2 Khz to 20 > Khz on "high". Exact frequency depends on where the pot is adjusted. > How can I calibrate this to be more precise, preferably in a simple way? Beat it with mains hum. This should work on the low range and at least part of the way up the high range. -- ~ Liz Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
| Phil Allison <pallison49@gmail.com>: Mar 01 11:56AM -0800 Liz Tuddenham wrote: =-=================== > > How can I calibrate this to be more precise, preferably in a simple way? > Beat it with mains hum. This should work on the low range and at least > part of the way up the high range. ** You need to explain that idea. The OP seems to have no test gear or clue. ...... Phil |
| Tinkerer <tinker5@anytime.net>: Mar 01 04:07PM -0500 On 3/1/21 12:04 PM, Tim R wrote: > Cheap USB microphone, laptop, Audacity? (Audacity is free recording software with lots of extras, does frequency, etc) Great idea. I have Audacity. I could just play the audio output and either capture with mic or feed into soundcard and then see what it is in Audacity. I think that's what I'll do, although I like Phil's suggestion of a DVM with freq counter, been keeping an eye out for one. |
| Tinkerer <tinker5@anytime.net>: Mar 01 04:09PM -0500 On 3/1/21 2:46 PM, Liz Tuddenham wrote: >> How can I calibrate this to be more precise, preferably in a simple way? > Beat it with mains hum. This should work on the low range and at least > part of the way up the high range. Not sure what that means, unless you mean a harmonic of 50/60 Hz. It might be possible to beat by ear if the PC generates the tone and I adjust the generator until it matches by ear, but I think I'm just going to use Audacity and/or a DWM with freq ctr as suggested by Phil. |
| Bennett <bjprice@cal.berkeley.edu>: Mar 01 09:09PM -0800 On 3/1/2021 1:09 PM, Tinkerer wrote: > might be possible to beat by ear if the PC generates the tone and I > adjust the generator until it matches by ear, but I think I'm just going > to use Audacity and/or a DWM with freq ctr as suggested by Phil. Google Online Music Tuner In the US the note A is generally considered 440HZ This one gives the frequency in Hz https://bit.ly/383gzou |
| Abandoned_Trolley <fred@fred-smith.uk>: Mar 02 10:01AM On 02/03/2021 05:09, Bennett wrote: >> going to use Audacity and/or a DWM with freq ctr as suggested by Phil. > Google Online Music Tuner In the US the note A is generally considered > 440HZ This one gives the frequency in Hz https://bit.ly/383gzou Speaking of which ... I believe some musicians are able to tune their instruments by using the dial tone from a landline as a reference. AT |
| Phil Allison <pallison49@gmail.com>: Mar 02 04:11AM -0800 Abandoned_Trolley wrote: ====================== > Speaking of which ... I believe some musicians are able to tune their > instruments by using the dial tone from a landline as a reference. ** But only after taking a huge dose of Meth first. ...... Phil |
| bilou <bilou@sfr.fr>: Mar 02 02:34PM +0100 On 01/03/2021 18:04, Tim R wrote: > Cheap USB microphone, laptop, Audacity? (Audacity is free recording software with lots of extras, does frequency, etc) If you have a PC with a decent sound card you don't need an audio frequency generator :-) |
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