That "Cylon" meter is kind of special, Bob and the team put a lot of effort into it so that it would be accurate and useful rather than just looking cool. Great vids as always!
Hi Tony, Very good explination how this amp works, you are a professional. I do restores of the series two for my hobby in Belgium. I think I have seen more than 40 amps in the last 10 years. What I replace is also the R102 (7,5 KOhm/2Watts), both because one out of 10 do drift to go open. Second I always replace both thermal feedback transistors Q118 - because again somethimes they are not good and you have thermal drift away (your amp is very good so no issue) but I see it with 10 % of the amps. Nice work ! Greets Flip
I have a mark 1 and I really needed this info to restore this ex. It did run last time I checked but has been quiet a long time and I don't want to risk my speakers. Thanks for great video and much needed info.
Tony, I just stumbled across this video. I'm trying to learn more about electronic design, and I really found this video super helpful. I love how you explain in detail the concepts of circuit design!
In today's world the TL071/72/74 should only be used in sub-wooferor and/or car audio application. The OPA2134 is a much better choice for audio. Op amps should ALWAYS be supplied by a regulated supply with at least two PS bypass caps of .1uf. (one DYI standard uses at total of 4 caps per PS rail, mounted as pairs. 4.7 & .1uf (parallel) where the power enters the board and a .1uf & .01uf (parallel) closest to the chip. I always wondered how to design home-made inductors for the Zoebel networks. That was good info.😉
Enjoyed the video, and appreciate the changes you made (as you explained them). I really like the quasi-differential design, if only because it’s much easier for me to follow the all-NPN design. 🙂
Tony, they can't see because schematics are mostly white, and the auto-exposure of the camera sets on the average of the image, and that is mid-gray, so all the whites turns into mid-gray. When showing schematics it would be nice when you compensated for that, but I know it would break your workflow. It could also benefit the exposure when the exposure is based upon the whole image, and not only the centre, but I don't know what it is set now. Compensating for a mainly white image means over exposuring 2 - 3 so called 'stops'. Another way is fixed exposure (manual, not auto), but then the lighting would need to be fixed too. You will see the effect the best when you put a schematic full in screen. Look at the picture, and shove a significant piece of black in the image. You will see the white of the schematic shift towards real white.
@ <a href="#" class="seekto" data-time="180">3:00</a> It's fun to put in the R-C components into a SPICE model to see how they may affect the frequency response if changed. Good mods on the opamp capacitor adds for sure. For a few minor power supply mods, I would also have considered bridging the AC secondary feed of the bridge rectifier with something like a .001uF capacitor to quell some diode switching noise, and also bridging the 2 main filter caps with a 0.047uF to reduce any residual high frequency noise that those caps may not be able to filter due to their inherent rise in internal inductive reactance vs frequency. Instead of leaving the thermal cutoff inline with the Line / mains power, I would have considered rewiring them to interrupt the power to the speaker protection module you added. That way, there's less added AC hum ( current is only feeding the protect module, so less hum is radiated) from those thermal sensors wiring floating around in the chassis, and it reduces the overall resistance of the primary line feed.
<a href="#" class="seekto" data-time="2422">40:22</a> - "Don't take the car out at night; you'll rear-end somebody, they'll sue us and we'll lose the house!" - Kevin Meaney
Doncha know Tony, we already all died, and this is a simulation... It's all because of the placement of those capacitors. Circuit board designers generally are not an engineer's friend. I worked on aircraft power systems, so I learned the intricate ins and outs and lightning strike bonding. Grounding is the most critical aspect quickly followed by component placement. 787 Flight Systems Computer - Power Conditioning Module is my design from the housing to the circuit boards.
Transzorbs on the input signal connections, quite a few would fail at the test stage - Supervisory Engine Controller for the 757, I didn't design it but tested and diagnosed faults.
<a href="#" class="seekto" data-time="555">9:15</a> I don't agree with lowering the current through zeners. As far as I know they are least dependant on ambient temperature when close to their Wattage. They run hot then, but like an oven for a time base oscillator, it is far above ambient inside, and ambient then is relatively ineffective. When cooler, they drift more.
That's one of the nastiest PCBs I have seen ! I like the power side of this with the input caps and transistor setup but I would redesign that PCB add your bits and some other improvements, then I think you would be left with a different beast with a good pedigree that would sound just fine. Is taking your precious signal and putting it into a PCB with a switcher on it a good idea ? you could ask our new friend 'Audiofile' LOL !.....cheers.
Thanks, Tony. Another good one, though I do take offence to the voice you used as what you thought I sound like.😂Edit: the second voice you used sounded a lot more like me!!! thanks… oh now you’re just trying to mock me the third time aren’t you!?!?😮…😊
I have been a highly dedicated audiophile since 1960, and involved for a while in sales, so I'm really surprised that I had never heard the term "Flame-Linear" before. It would be interesting if you would contact Bob Carver, for his opinion your video, and let us know.
I was hoping you would do the current sharing output check Step #9. Curious about the condition of the original outputs. This is one check I don't like doing. I have a ton of those 909 outputs if you need them.
Hi Tony. I recently saw your video on the HK PM665. In it you mention the unit needed a complete washing. Could you fill in a newbie as to what a complete washing entails? Interested in your approach to cleaning badly taken care of gear. Thanks.
@@xraytonyb Some production designs on other amps have placed them on the capacitors, but to be more efficient they would be installed as close to the point of load as possible. Dave @ EEVBLOG had a good video on where to place caps to filter out noise, and closest to the component load proved to be the most efficient placement, just like your cap placement on your opamp mods.
@@kenielsen Just as a question, do know of any amp designs that use a uF range cap bridged to the main filter cap? I know I have seen some with nF range value caps , but never another uF ranged one.
Nice conservative changes and safety fixes. The LED display is kind of boring. Maybe change them out to more vibrant colors of green, yellow, red. That amp should sell fast, and would be great for a Texas dance bar.
Sorry to be that guy 🙄 (<a href="#" class="seekto" data-time="138">2:18</a>) but the schematics were painful to read even in 1080p. It's not just the resolution, the white is blinding. 😕
