Hi Shawn,
Thank you. No rush. 😉
You are doing a proper restoration. This will keep you out of trouble for a while.
-Chris
Thank you. No rush. 😉
You are doing a proper restoration. This will keep you out of trouble for a while.
-Chris
New Kids On The Block
Thanks for the good words Q, latala & everyone else!
I had a rendezvous today to pick up the On Semi Outputs but only half of them showed up after losing the previous shipment?
Ouch! The rest have been taken care of (?) and here is a pic of the new kids on the block. Just another little delay.
Shawn.
Thanks for the good words Q, latala & everyone else!
I had a rendezvous today to pick up the On Semi Outputs but only half of them showed up after losing the previous shipment?
Ouch! The rest have been taken care of (?) and here is a pic of the new kids on the block. Just another little delay. Shawn.
Attachments
Hi Shawn,
That's a happy looking crowd there. I'll bet they are looking forward to making music. 😉
-Chris
That's a happy looking crowd there. I'll bet they are looking forward to making music. 😉
-Chris
Happy Looking Crowd...
I wish they were from the same batch? I'm certain a totally different date code will show up in the next shipment of 10. In this design it may not really matter but still...? Kinda sucks?
I picked up most of the remaining semiconductors today and the balance of passives. I just got home and the soldering iron is warming up and the beer is cooling off.
I tried shopping the front metal plate out today to see if someone will put the love into resurfacing it and anodizing it but no luck yet. I want to gold color tint the anodize treatment if I can to make it a one-of-kind, you know, both inside and out?
Cheers,
Shawn.
anatech said:
I wish they were from the same batch? I'm certain a totally different date code will show up in the next shipment of 10. In this design it may not really matter but still...? Kinda sucks?
I picked up most of the remaining semiconductors today and the balance of passives. I just got home and the soldering iron is warming up and the beer is cooling off.
I tried shopping the front metal plate out today to see if someone will put the love into resurfacing it and anodizing it but no luck yet. I want to gold color tint the anodize treatment if I can to make it a one-of-kind, you know, both inside and out?
Cheers,
Shawn.
Hi Shawn,
One-of-a-kind is always good. They have a show at the CNE for that stuff, sadly much of it is mass produced these days. 😀
Don't worry about batch numbers so much Shawn. I've been looking at consistency with On-Semi's products. I must say that it's much, much better these days. With the newer products, I'd say that the process is very much in control. Have a look at the stragglers and compare to your early lot.
-Chris
One-of-a-kind is always good. They have a show at the CNE for that stuff, sadly much of it is mass produced these days. 😀
Don't worry about batch numbers so much Shawn. I've been looking at consistency with On-Semi's products. I must say that it's much, much better these days. With the newer products, I'd say that the process is very much in control. Have a look at the stragglers and compare to your early lot.
-Chris
anatech said:
I remember ordering direct from Philips when they were located in Scarborough (Toronto). I used to expedite billions of pieces back in the day...what was the lead time when I finished that gig...1995...32 weeks!?
I don't know who makes these but they are "good" quality 1% from the Orient. I think the Philips I used to order were from Malaysia back in the mid 90's. I think these are from China but I'm not 100%.
Lately, I've been eye-balling the .1% they now stock at Parts Connection (PCX) but not for this job, not yet.
Cheers,
Shawn.
Hi Shawn,
Close tolerance parts may not be what you want. Look at the tolerances in your caps and active parts. Possibly for gain setting components. Always keep in mind the voltage developed across the feedback resistor and go higher than you think you need for power. You may then need a couple pieces in series or parallel.
-Chris
Close tolerance parts may not be what you want. Look at the tolerances in your caps and active parts. Possibly for gain setting components. Always keep in mind the voltage developed across the feedback resistor and go higher than you think you need for power. You may then need a couple pieces in series or parallel.
-Chris
Hi Shawn,
I forget the rails, but let's assume they are +/- 60 VDC. We will assume a perfect amp with no supply sag (like clipping into an open load) and no loss due to transistors. So you have sine wave of 60 V peak just before clipping. This will appear across the feedback resistor from the output to the error amp. (simplifying). Assuming 10K, the resistor will dissipate about 180 mW. If you are clipping the power will be higher still. The use of a 1% carbon resistor is clearly unwise. This also indicates a possible temperature rise in the part.
Real life. The Lightstar has 125V rails with a 9.1 K resistor as the feedback resistor. That means that it's possible for it to dissipate in excess of 0.86 W in clipping. I've seen them burn a hole (large) in the PCB. I still have one example around here somewhere. Of course the amplifier also eventually failed.
-Chris
I forget the rails, but let's assume they are +/- 60 VDC. We will assume a perfect amp with no supply sag (like clipping into an open load) and no loss due to transistors. So you have sine wave of 60 V peak just before clipping. This will appear across the feedback resistor from the output to the error amp. (simplifying). Assuming 10K, the resistor will dissipate about 180 mW. If you are clipping the power will be higher still. The use of a 1% carbon resistor is clearly unwise. This also indicates a possible temperature rise in the part.
Real life. The Lightstar has 125V rails with a 9.1 K resistor as the feedback resistor. That means that it's possible for it to dissipate in excess of 0.86 W in clipping. I've seen them burn a hole (large) in the PCB. I still have one example around here somewhere. Of course the amplifier also eventually failed.
-Chris
Feedback & resistors
Chris,
This particular amplifier was boasted by crown as deploying 1% resistors in the feedback loop. They claimed it as a feature!🙂
Further, but I do not have all the documentation yet, there are four adjustable pots for off-set and two "wild-card" resistors that can be tested and selected to balance this amp. I could be wrong but I think there is even more documentation about calculating & adjusting the feedback on the Crown DC300A as prescribed by Crown.
I have not seen it yet, but I believe one of the sections in the documents that Joe has mentioned, addresses the particulars of adjusting the feedback in these amps.
I know for certain it was addressed in the DC300A II. 🙂
I have only "heard" of such things, I have not yet seen them but they would shed great light on these issues you point to.
Scan away Joe, we all need the scoop on this hunk of love! 😀
Cheers,
Shawn.
Chris,
This particular amplifier was boasted by crown as deploying 1% resistors in the feedback loop. They claimed it as a feature!🙂
Further, but I do not have all the documentation yet, there are four adjustable pots for off-set and two "wild-card" resistors that can be tested and selected to balance this amp. I could be wrong but I think there is even more documentation about calculating & adjusting the feedback on the Crown DC300A as prescribed by Crown.
I have not seen it yet, but I believe one of the sections in the documents that Joe has mentioned, addresses the particulars of adjusting the feedback in these amps.
I know for certain it was addressed in the DC300A II. 🙂
I have only "heard" of such things, I have not yet seen them but they would shed great light on these issues you point to.
Scan away Joe, we all need the scoop on this hunk of love! 😀
Cheers,
Shawn.
anatech said:
These 10k resistors on the original printed circuit board of the DC300A are high power and 1%. I adjusted slightly buy using a 2watt version @ 2% tolerance! I think I'm digging what you are saying but if you look closer at the actual printed circuit board images, not the schematic, you will see some of the actual changes Crown embraced even in the early stages of REV changes.
I have used allot of components of the original PCB that are not present in the schematic that "we" have. Also, I see now, a requirement for other components that are on the schematic but lacking in the original PC board. It is a hard mix but I think I'm on the right track.
If I had full errata on this thing, it would help allot but I have already learned soooo much about this amp by etching the PCB and loading the components...I will have to write my own manual when I'm done.
You folks are like a ratchet with your comments and suggestions I hope you all keep it up so I can squeeze the wine out these grapes.
I know, I know...cooking wine for some but fine drinking wine for others?
...soldering iron is crying in neglect...more later
Shawn.
anatech said:
I personally know and hang out with one of the few full-time staff that run and organize that event. I always get free tickets for my MOM, wife & whoever. Funny you should mention it. Chris, my friend, you always trigger something acute. Good times!
Shawn.
Attachments
Hi Shawn,
Looking pretty good. Are those Miller inductors?
I enjoy going to the One-of-a-kind show. It was more fun in the early years. Glen Williams is very close to me, wonderful area for artisans. If you haven't made it up here, I recommend it highly. More fun in the summer on a Saturday when you can hit the farmer's market as well. You can buy Moose sometimes.
So when is that craft show on this year?
-Chris
Looking pretty good. Are those Miller inductors?
I enjoy going to the One-of-a-kind show. It was more fun in the early years. Glen Williams is very close to me, wonderful area for artisans. If you haven't made it up here, I recommend it highly. More fun in the summer on a Saturday when you can hit the farmer's market as well. You can buy Moose sometimes.
So when is that craft show on this year?
-Chris