- Schematic for 1974 GM car radio needed - 4 Updates
- Think twice before you buy Duracell batteries - 1 Update
- Splattering solder into eye? - 1 Update
| ohger1s@gmail.com: Sep 19 11:13AM -0700 I only need the immediate output stage. This had a blown DS501 and I want to check the bias on this germanium transistor. This came out of a '74 Caddy but all GM car radios used the same output system so if anyone has a scan of any of them or a working link I'd love to get a look at it. |
| whit3rd <whit3rd@gmail.com>: Sep 19 02:26PM -0700 > This came out of a '74 Caddy but all GM car radios used the same output system The old Sams Photofact series covered lots of car radios; check to see if your local library had a subscription, or can get an interlibrary loan. Or, there's online merchants (or eBay) if you can figure out which folder number you want. Sams is still in business, <https://www.samswebsite.com/> |
| ohger1s@gmail.com: Sep 19 07:19PM -0700 On Monday, September 19, 2016 at 5:27:10 PM UTC-4, whit3rd wrote: > local library had a subscription, or can get an interlibrary loan. Or, there's > online merchants (or eBay) if you can figure out which folder number you want. > Sams is still in business, <https://www.samswebsite.com/> A lot of trouble for doing a favor for free... But you reminded me that somewhere I have (had) a box of old Sams books that just covered car radios. There's a chance I pitched the whole box in the dumpster a few years ago. I'll spend 15 minutes tomorrow checking storage where they are/used to be. |
| jurb6006@gmail.com: Sep 20 03:23AM -0700 Just turn it down. At full class A bias the circuit is capable of 8.9 watts into 8 ohms. Not all transistors could take that so many were set lower. Realistically it is hard to hear the difference between 8.9 watts and 5 watts. Plus, there is some amount of DC on the speakers so if they are not stock they might not like that DC. I know I blew a pair like that a long time ago. If you check the DC resistance of the output choke you can do a few calculations. It is probably 1.2 ohms and they call for one volt across it. For the stock speakers that were actually ten ohms, the DC did not bother them, but if they have been replaced you want that bias lower or else put a blocking capacitor in series. I would say that you don't want any more than a volt across that output choke. If you want more power get a power booster. Also, since it failed ad they never do, and the age, I would suspect the cap across that output choke. Those are alot higher value than we are used to these days, I don't remember specifically but they might be 10 uF or something like that. If that goes open the output transistor is very vulnerable to inductive spikes. Being across the choke, very few caps checkers will check their ESP, bitching about a short circuit. So you have to disconnect it. My scope based one will but those mean some building. You have to have a known impedance of a known voltage of a square wave and that requires prints. It might be useful later but not enough for just one project. Anyway, using the output choke DC resistance as a guide, set it to somewhat less than one amp and see how it works. It might be just fine. I the speakers have been replaced they might be four ohms or at least have a lower DC resistance in which case you have to set it even lower. If stock speakers which will be ten ohm, put a bit less than a volt on it and your output transistor will be dissipating about 12 watts all the time. Even the cheaper ones can handle that. There were some of those cars that had faders and more than one speaker. Those had the bigger output transistors and the heftier chokes, and were of course biased higher to get that couple of extra watts. Check that cap, and then get say 750 mV across that coil and see how it sounds. If it sounds good, ship it. |
| Roger Blake <rogblake@iname.invalid>: Sep 20 01:36AM > Ditto for you. Your mother was a hamster and your father smelled of elderberries. -- ----------------------------------------------------------------------------- Roger Blake (Posts from Google Groups killfiled due to excess spam.) NSA sedition and treason -- http://www.DeathToNSAthugs.com Don't talk to cops! -- http://www.DontTalkToCops.com Badges don't grant extra rights -- http://www.CopBlock.org ----------------------------------------------------------------------------- |
| Jon Elson <jmelson@wustl.edu>: Sep 19 03:46PM -0500 Benderthe.evilrobot wrote: >>> Has anyone ever actually been unlucky enough to get solder splattering >>> into their eye? I've had it hit my leg, hand, and face, but never in my >>> eye. How bad is it? I've had microscopic specs of solder splash in my eyes a few times. At least, I THINK they were solder, they felt different than having flux get in my eyes. If the spec is small enough, the film of water on your eye cools id down pretty quickly. I may worry less about this than some others as I wear eyeglasses all the time and they have wide enough leses as to shield my eyes fairly well. > When harvesting components with a pencil blowtorch; the spitting can be > hotter - but I hold the board looking at it edgewise, the spitting goes > sideways and nowhere near my face. I would ALWAYS wear some kind of protection when doing this kind of work. Jon |
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