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Member Since 04 Nov 2013
Offline Last Active May 14 2014 04:11 PM

Posts I've Made

In Topic: D150- One Channel Down!

14 May 2014 - 04:01 PM

Hello again, it's been a while!
Today I have good news and bad news.
The good news: My D-150 is up and running perfectly.
The bad news: I don't know why!

I finally got it together and got hold of an oscilloscope, but first, I figured, I'd change a couple of suspicious caps and the diode I broke while poking around. So I set up a lovely work table, got all my tools together (including the spiffy new scope), and satrted by swapping out those couple of parts. So far so good, now I can get started with the scope, I thought. So I hooked it up and put a sine wave through the amp. Nuthin'. Hmm, am I doing this right? So I hooked up a speaker to the good channel, and sure enough, a nice clean 1000Hz sine wave was coming through. Ah, heck, I'll try out the bad channel, too, I thought. Guess what? A nice clean 1000Hz sine wave was coming out there, too. ¡Que rico suave estoy!, I'm thinking, 'cept for two things: I have no clue what I did right, and I didn't learn a dang thing! Good thing I've got a couple more broken amps lying around.

I humbly thank this forum, and y'all wish me better luck next time, OK?


In Topic: D150- One Channel Down!

06 December 2013 - 10:17 AM

Ah, today I am laughing. Those of you who have read the above know the story, but here's a synopsis anyway:
My old D150 broke. I started a thread here in the hope of getting advice on fixing it, where I lamented that the schematics and PC layout diagrams on the Crown site are illegible. After pulling out a lot of hair, trying to decipher the scans, I got a tickling sensation telling me that I may actually have those diagrams somewhere. Now listen, I am chaos personified, but I swear, I found an ancient copy of the amp's schematic in an old carton full of miscellaneous mixed papers within seconds, as though some mystical force were guiding my hand. Wit that and a lot of patience, I was able to more or less re-draw the PC layout, so that I could begin troubleshooting. But I wasn't so sure that my drawing was accurate, so I began with some trepidation.

Now I'm getting to the punchline:
Yesterday, I had occasion to look through that same box of old papers, for something entirely unrelated. This time I got all the way down to the bottom of the box, and what did I find there? Ha! The rest of the Crown document, containing parts lists, blowup-drawings, and two lovely, pristine drawings of the PC oard with all its components. Here's links:


The link to the drawing that I made myself is now dead, because I'd hate to have anyone burn up an amp as the result of some mistake I made...

Now then: I STILL haven't found the problem in this amp. I have done a lot of checking, and found the following: No DC at output. I've checked output x-sistors, drivers, the IC, diodes 210 and 211, none of them can be causing the problem. I have checked voltages at several points and definitely found discrepancies between the two channels. But for one thing, I haven't got an oscilloscope (working on getting one but I'm a Mac user and all the ones I see and might be able to afford only work with PC), and for another, basically none of the voltages I read match up with the schematic. I'm thinking that's down to leaky elkos, so I think I'll recap the beast and see what I get. Meanwhile, your tips are very welcome!


In Topic: D150- One Channel Down!

18 November 2013 - 01:05 PM

Hi again everyone.
Soo... I'm getting around now to figuring this amp out. First I decided to make a legible diagram of the PC layout, and here is what I've got so far:


the linked diagram has not been checked by a real engineer, so please don't use it as a reference yet! I haven't checked it for accuracy, nor for proper PNP/ NPN orientations and the like.

For the moment, here's my question:
I'm having trouble reconciling the schematic (see above posts) with both Crown's (nearly illegible) layout diagram and the PC board in the actual amp, which I have in front of me. To be precise, it's those transistors Q102 and Q202. I'm aware that they are in a TO-92-18R package, which would make their pinout C-B-E as opposed to the usual E-B-C, right?... but still, the schematic has their bases going directly to pins 1 and 13 of the IC, which doesn't seem to be the case in reality. Also, there are two diodes on the board which seem not to appear on the schematic, as far as I can tell, in fact bridging those very two pins 1 and 13 with the collectors of those very two transistors. What gives?

THANKS AGAIN! (he screamed... sorry...)

In Topic: D150- One Channel Down!

14 November 2013 - 06:54 AM

OK- working on getting this schematic into a more usable format, but for the moment here's a link to a photo of it:

In Topic: D150- One Channel Down!

13 November 2013 - 07:14 AM

Ha! now here's something:
Somewhere, way back in a corner of my mind, I had a feeling I'd seen a D150 schematic in my old junk. So I opened the box of papers I'd been avoiding for aeons, and lo and behold, stuck in with the schematic for my Ampex SA-10 was a D150 schematic, not perfect but much better than the one on the Crown site. I have no idea where or when I got it, but it's on US- sized paper, and I haven't lived in the US for over 20 years, so it's at least that old. I'll take it to the copy shop today and get a hi-res scan, and post that here. I hope it helps someone out there!
All the best,