The channel with the 2SC1116s was the original version, later 2SD555s. My NINE+ had the ARC4700 or ARC4800 in it which were the Fujitsu xsistors. These were the bean counter xsistors. As was the non-Bando power xfmr.
Both of mine are now all me, can't tell the difference except for the xfmr. Does your amp have covers over the xsistors, if not, bean counters. My + does not.
Craig
Both of mine are now all me, can't tell the difference except for the xfmr. Does your amp have covers over the xsistors, if not, bean counters. My + does not.
Craig
All sorts of different types of resistors!
OPAMP is an AD823AN with a date code of 0345... 45th week of 2003?
OPAMP is an AD823AN with a date code of 0345... 45th week of 2003?
Those are not the factory output terminals. The factory terminals were NOT binding posts and both were red in color because neither are ground. So I would say somebody other than factory was in yours. Even the later factory repair work wasn't that sloppy from my experience. It's all that little stuff that makes it easier to strip and start over.
Craig
Craig
I can't make out who the manufacturer of the transformer is, but at the top of the label stuck to the side of it says 'Made in Canada.'
No covers on my transistors, either side. I'd be curious about what that part looks like... might be able to have one made up through a supplier at work!
P.
Except for the opamp that looks to be all original. Even though the AD823 was JB's choice of modern opamps it still needed to be selected to operate at the 20VDC supplies. I just reinstalled the LF412A in mine.
Craig
Craig
Hi Craig,
How would he go about selecting an op amp for higher supplies? Case temperature or current draw?
-Chris
How would he go about selecting an op amp for higher supplies? Case temperature or current draw?
-Chris
Chris,
I've never done it. I'll have to do some looking. I think he used a dual tracking power supply and turned the voltage up while monitoring the distortion.
Craig
I've never done it. I'll have to do some looking. I think he used a dual tracking power supply and turned the voltage up while monitoring the distortion.
Craig
Chris,
Here's your answer for selecting the opamps, from JB.
"Hook up a standard gain of 10 circuit with a variable tracking power supply (up to +/- 25V). Drive the opamp to say about 10 volts RMS at 1KHz with the supplies at +/- 18V to start. Null the output on a distortion analyzer. While watching the residue in X-Y mode, slowly turn the supplies up until the output shows cusps beginning to form on the residual. At that point, note the supply voltage. There's your limit."
Craig
Here's your answer for selecting the opamps, from JB.
"Hook up a standard gain of 10 circuit with a variable tracking power supply (up to +/- 25V). Drive the opamp to say about 10 volts RMS at 1KHz with the supplies at +/- 18V to start. Null the output on a distortion analyzer. While watching the residue in X-Y mode, slowly turn the supplies up until the output shows cusps beginning to form on the residual. At that point, note the supply voltage. There's your limit."
Craig
I've starting thinking about the insulating pads under each transistor. Mica and compound can get goopy, and it I grab the amp wrong to move it, I can get white paste everywhere; no covers on the transistors! I think I've narrowed it down to two parts,
These silicone pads look nice. Dielectric breakdown at 4500 VAC, resistivity of 10^11 ohm-meters, and a thermal conductivity of 1.0 W/m-K.
These phase change pads look interesting. It's a compound supported by a fiberglass core which is rubbery at room temperature but flows like paste above 65 °C. Dielectric breakdown at 300 VAC, resistivity of 10^10 ohm-meters, and a thermal conductivity of 0.8 W/m-K. Material returns to a 'solid' state at room temperature.
Any thoughts on these products, or pointers to better bits?
These silicone pads look nice. Dielectric breakdown at 4500 VAC, resistivity of 10^11 ohm-meters, and a thermal conductivity of 1.0 W/m-K.
These phase change pads look interesting. It's a compound supported by a fiberglass core which is rubbery at room temperature but flows like paste above 65 °C. Dielectric breakdown at 300 VAC, resistivity of 10^10 ohm-meters, and a thermal conductivity of 0.8 W/m-K. Material returns to a 'solid' state at room temperature.
Any thoughts on these products, or pointers to better bits?
Hi Philip,
I still use mica and paste. If you put the proper amount on, only a little bead squeezes out when you tighten the transistors. Those fasteners are not cranked down, I think TO-3 parts are 8 inch-lbs or something like that. TO-220 parts are 6 inch - lbs. I may have the units wrong, but this is covered in an On-Semi app note concerning the mounting of their various packages.
The phase change insulators are supposed to be the best thing to use. But the amp was designed for goop and mica, so you don't need the last bit of heat energy to go out.
-Chris
I still use mica and paste. If you put the proper amount on, only a little bead squeezes out when you tighten the transistors. Those fasteners are not cranked down, I think TO-3 parts are 8 inch-lbs or something like that. TO-220 parts are 6 inch - lbs. I may have the units wrong, but this is covered in an On-Semi app note concerning the mounting of their various packages.
The phase change insulators are supposed to be the best thing to use. But the amp was designed for goop and mica, so you don't need the last bit of heat energy to go out.
-Chris
I just never liked the mess associated with the paste, or maybe I'm doing something wrong. For 20 of those fancy phase change pads, I'm looking at $7.50, so not breaking the bank. What I'm more concerned about is the electrical isolation... But I should be OK there, too.
That's interesting... metal films, carbon comps, and old-school tubular carbons all intermingling? Didn't look stock to me with that mixture! Though maybe this was done for sonic reasons... ?
Hi Philip,
Carbon film was and is the common resistor to find in equipment. Carbon composition is normally used for RF and gate / grid stopper resistors where absolute value is less important than non-inductive traits. Metal film resistors are a new thing, in 1974 they were extremely expensive. Back then a 5% resistor was high accuracy, 10% in good equipment and normal resistors were 20%. I kid you not! 2% resistors back then were super high accuracy and 1% was almost unheard of except in military and instrumentation applications. Good meters were 5% accurate and very good meters were 2% or 2.5%. It was a different world back then. No internet either.
-Chris
Carbon film was and is the common resistor to find in equipment. Carbon composition is normally used for RF and gate / grid stopper resistors where absolute value is less important than non-inductive traits. Metal film resistors are a new thing, in 1974 they were extremely expensive. Back then a 5% resistor was high accuracy, 10% in good equipment and normal resistors were 20%. I kid you not! 2% resistors back then were super high accuracy and 1% was almost unheard of except in military and instrumentation applications. Good meters were 5% accurate and very good meters were 2% or 2.5%. It was a different world back then. No internet either.
-Chris
All excellent points I didn't consider, I laugh when I see old capacitors spec'd at +/-25%. My goodness!
I keep Dale carbon comp mil spec and Yageo metal film parts on hand for projects, 1/4W devices, and have already replaced the smaller capacitors with bits from my Panasonic FC and FM stock.. Is there any benefit to be gained from replacing these resisors? I noticed in the schematic for this amp there some values were marked as hand picked!
I've gone through and verified the sender's diodes work as expected, between 20V and 20.2V as measured.
I'm not loving how I have to fight with the magnet wire in order to inspect the power supply PCB. I almost feel as though I need to remove the transformer to get a look look at anything... except all the power wiring is soldered to the thermal switches and I've run out of hobby time for tonight.
From what I can see, some of the magnet wire pads have lifted off the PCB, and they're starting to take traces with them.
I want to add a series of screw-down terminals to which the magnet wire will enter, and exiting will be some XLPE stranded wire that will go to the PCB.
Heck, I'll replace all the wiring with stranded XLPE. I love this stuff
Short-term goals: need to buy a pack of quick connect crimps and fix the solder-everything-together patch which was done in the past, maybe try to test the thermal switches, and refurb the PSU PCB. I'd also like to connectorize the fan wiring. It's getting old having to keep both halves of the chassis together.
P.
From what I can see, some of the magnet wire pads have lifted off the PCB, and they're starting to take traces with them.
I want to add a series of screw-down terminals to which the magnet wire will enter, and exiting will be some XLPE stranded wire that will go to the PCB.
Heck, I'll replace all the wiring with stranded XLPE. I love this stuff
Short-term goals: need to buy a pack of quick connect crimps and fix the solder-everything-together patch which was done in the past, maybe try to test the thermal switches, and refurb the PSU PCB. I'd also like to connectorize the fan wiring. It's getting old having to keep both halves of the chassis together.
P.
Hi Philip,
Well, those were the "good old days".
The things you are running into are my chief complaints with that amplifier. By all means, find a way to connect the wires and prevent further PCB damage. You might consider using a heavy plug and socket for those wires. Some connectors will allow you to screw the magnet wire down into the plug. Trim the wire back a little if you see any signs that it is getting ready to break. Using connectors for the fans and temperature devices is the only sane way to deal with everything.
Stand back and take a look at this amplifier and figure out what leads can be connected in common. The thermal cut outs are already set up for the 0.25" push-on connectors. Once that has been done you might be able to enjoy working on it.
-Chris
Well, those were the "good old days".
The things you are running into are my chief complaints with that amplifier. By all means, find a way to connect the wires and prevent further PCB damage. You might consider using a heavy plug and socket for those wires. Some connectors will allow you to screw the magnet wire down into the plug. Trim the wire back a little if you see any signs that it is getting ready to break. Using connectors for the fans and temperature devices is the only sane way to deal with everything.
Stand back and take a look at this amplifier and figure out what leads can be connected in common. The thermal cut outs are already set up for the 0.25" push-on connectors. Once that has been done you might be able to enjoy working on it.
-Chris
I haven't read word for word everything since I posted yesterday but I want to comment on two things I noticed. First the xsistor insulators, every old amp that I've tried using the "new" insulators often oscillated, Phase Linear 400 and Quatre come to mind. So, like Chris, I usually stick with mica and goop, a little more messy and time consuming but if your amp oscillates you'll be doing it anyway and you wasted a few $ on insulators that can NOT be reused. Second the resistors, most are carbon comp. because they're cheap and 5% tol. is good enough. The few metal films used are in the feedback network and I'm pretty they're used just because of their 1% tolerance.
Another thing on the xfmr secondaries and the broken solder joints in my NINE+. Somebody got real lazy and didn't remove enough of the mag wire coating/insulation which makes for a real crappy solder joint. If you remove the PS board clean those xfmr leads.
Craig
Another thing on the xfmr secondaries and the broken solder joints in my NINE+. Somebody got real lazy and didn't remove enough of the mag wire coating/insulation which makes for a real crappy solder joint. If you remove the PS board clean those xfmr leads.
Craig
Hi Craig,
Yes, completely agree. The enamel can be difficult to take off, try sandpaper or steel wool. If you use steel wool, cover the amplifier with a plastic bag to keep that stuff out of there.
The test to see if the wires are ready for use is to tin them. If they accept the solder without trouble you are good to go. Even if you plan to use a screw type mounting, those leads should still be tinned.
-Chris
Yes, completely agree. The enamel can be difficult to take off, try sandpaper or steel wool. If you use steel wool, cover the amplifier with a plastic bag to keep that stuff out of there.
The test to see if the wires are ready for use is to tin them. If they accept the solder without trouble you are good to go. Even if you plan to use a screw type mounting, those leads should still be tinned.
-Chris