Відео

I don't believe that the blown meter lamps that you pulled out were original; they were covered with green Mylar sleeving that would typically be on AKAI lamps (and on a few other makes but not Pioneer). It gives a nice subtle green glow. I wish that I could find a source for purchasing some stock but I've never been able to find it.

Hola que transistor tr output de salida tiene este amplificador?

Great work! I would have made an offer but the shipping would kill me!! All the best,

How much do you think he can get for that?

If I remember correctly, you will get maximum heat dissipation in the output transistors on an analog amp at about 40% of rated output, because at that point, you have the highest product of current and voltage across the transistors. It should really cook then.

Harmon Kardon used to market their amps (even the smaller ones) as having high current capacity which would probably account for the number of caps in the circuit design.

Nice to see you back, this is a interesting specimen. 1983-1986............Not HK's best years for QC. Added a film cap to every service cap, hmmmmmmmmmm. Have every right to complain about that 1/2 ass white compound Goop. Never ever seen that light Blue stuff you purchased, very $$$$$$$$ Hell yes, those are big holes and little plastic support. Thanks for pointing out the thickness of the legs on those Burgundy colored Caps.

I like eating the thermal paste ! Reported you to Dig-Key LOL Without speaker protection you risk getting DC at your speakers,/ This could have been the cause of the transistors blowing as they took out the speaker (s) The shipping cost to the US makes it kind of problem

From where I'm sitting the problem with the transistors not sitting flat on the heatsink is due to the heatsink not being flat. There are signs that the heatsink is very slightly distorted, I would have been tempted to try to correct that so you don't need so much heatsink compound to fill the gap. It's amazing that it lasted long enough to dry out the old compound, those transistors must have been very robust but not indestructible !

Thanks Trevor enjoyed the video, all the best

You can't replace those output transistors, , you are going to just gerry-rig the unit to work correctly which in my opinion is not fixing it correctly The manufacture never intended for that unit to work in 50 years , theyr knew SMD would replace hold through components I worked in electronic manufacturing years ago, and all that electronics is 100 percent oblate by today's standards Why did you choose that transistor as a replacement ? This is constructive criticism

I used highest thermal conductivity compound with Peltier coolers. It is very effective, but after e while it was impossible do remove coolers from the heat dissipator. The ceramic in the compound was like cement. I had to break the coolers.

Bad work this time, very bad. You did not change any of the resistors on the vertical board??? I saw so many broken, there is literature and articles about them over the whole internet. I just switched it on for testing a few times and they blew, blew some transistors nearby. This amp could have also been thrown in the bin, if you use it like that, it will kill itself anyway, waste of time for a bad job that will maybe hold a few more months. Sad for the unit, I like those units, but this is not a lasting repair, I would not suggest ANYONE to buy this or run it like this. This is a receipe for desaster, the knowledge to work on 870 is clearly not there. And the fuse cover must be spread apart, and not pushed together, dont ask me how I know but I tried a bit too hard the wrong way, very flimsy board that is. Also the instruction is not very good, because the four metal covers dont fit with the bigger transistors that he used, so not sure if he left them out or bent them or what, not very clear video and unclear in many places. He said in the end he did not do it, how can you make an instruction video where half of the work is not done. Sad, could have been a proper video for 870 repair and maintenance, the crusty paste is something I also came accross, but if you go after that video, you can leave it as it is anyway, will not make any difference on the result, the 870 will fry itself and that was it. Then it is better not invest work and let it die than to make a bad job and let it die anyway. No care taken here.

Never saw that style of transistors before.

Another good design assembled poorly. Will make someone happy now. I actually bake sinks with transistors installed at 100°C in the oven and torque them down while still hot, compounds get runny and fill the gaps, while length contraction ensures they stay tight at high operating temperature. Bit tricky, but works great, especially with class A and high bias AB fet outputs.

Always loved the look of the plain box style amps.

When I saw the two sets of big capacitors I was thinking it might be class G bias with a twin split power supply rail. I know Kenwood, Carver, and Hitachi did those designs. Have to see if Hifiengine has a schematic on this amp, would like to see the roadmap on this one. The emitter resistors may have gone up in value due to the heat and abuse, that might account for the drop in wattage. Then again, it may just be the way it is. Thanks for the ride along on this one.

Great video! It was nice that there were some good replacement transistors available. Should give someone lots of years of service now.

Where did you buy the transistors from?

I believe a lot of the hk stuff in that era used direct coupled low negative feedback stages. So, the only limiting factor for frequency would be the transistors chosen for each stage. Some of them even had ultra wideband printed right on the front.

What the heck happened last Friday I was worried about you eh !

hi would you know where i could get the switch that you replaced

Just wondering, were you can buy the stop and start switch.

Gloves, really? 😅😂

Hello, great video 👍I have the same amp to repair for my rock-ola 474 juckebox do you have the list with the values ​​of the capacitors that you have changed it will help me a lot Thank you

We called those round things, records. 😊 great video. Thanks!

Really enjoying this content! thanks

Very interesting and amazing repair. This video is of special interest account I have this (SA)-6700. It looks mostly original other than the led upgrade, and the main caps have been changed to larger Elna 100v 15000 uf caps. What are the advantages of this , and is it even safe? Looks like it has all the Nippon Chem-con.

good god .. honestly it like watching a monkey try to type on a typewriter

I'm not sold on the replacement LEDs for the most part for the same reasons you quote. The AC/DC issue, the point source, the colour of the light... I'd much rather have new incandescents myself.

We have the same workbench. I use a grey doormat as a work surface too! Also the little green ruler mats!

Canon printers are junk!

Sony best stuff was really good stuff. They spared bo expense back in the day. I have the k75 from this series. It's the three head, dual capstan, with tone assisted record calibration. No direct drive though, and with led meters instead of the lcd. It really well made stuff.

Ah Sears, many things that Sears had was built in Sanyo factories ( these in south corea) at least the cheap ones . But at the same time they build many quality things ,as many JVC things , like camcorders , VCRS (vhs)......believe me , many panasonic ( ex NATIONAL in the first times)Vcrs share things with Sanyo . And some Sanyo VCRs where build with more quality and image than Sony , i know because i had two 4 heads stereo nicam VCRs ( vhs) one sanyo a one sony , and sanyo had more build quality than Sony that had many plastic gears and mechanics sounded louder, but both had good image quality .There where in those times a family relationship between those two brands. The Sanyo was the poor Panasonic (technics) parent, but they build some cheap and with some quality degree audio things that sounded good!

Hola mister trevors bench. Lo felicito por muy buen video y también pedirle de favor que si tiene el PDF del manual de servicio me lo pudiera pasar . gracias

What if it does go into protect? Mine clicks multiple times as i turn it on. I can only get music from zone 2..... not the other speaker ports. Please help.

Whatever happened to that Citation 12?

The mass turntable idea comes from when the motors weren't electronically controlled. It's a moot point now. There is no need.

So I believe I had this amp,bought it in the late 70's, used it till it went out in the late 80's. I thought I remembered it rated at 50 wps and also having a start up breaker that took like 5 seconds till it would click and let sound on. I didn't see that with yours here. Great video and thanks.

Go NADs!

Is there any difference betwenn models bdv e2100 and hdb e2100?

A rare Xerox branded custom Fluke meter made for Xerox, So cool!

That amp is a beast for 40 a side.

Too bad they didn't include high pass filtering. Maybe the next models do. Well, replacing the fuse as I am sure you know Trevor that doesn't negate the issue with why. 😂 See these caps...you know what I 'm thinking.... So, Trevor I'm going to assume you'll rectify the bare wire wrapped with tape etc. You, may, as we aren't at the end yet but to err on the side of caution I'd replace the drive transistors.

I have the 6500 which I have been using for about 6 months or so and now plan on refreshing - caps etc., so this should be an interesting watch. Thx for video!

I have this amp and it's not working at all. It has power but I get no signal coming through. So far I only had a quick look at it, however, so I will finish watching this clip and see if it is of use in my case.

Very good output transistors, they resist the torch!

I own every BOC CD. I used to record them on my Harman Kardon CD 291 cassette deck. People couldn't tell the difference between the tapes and the CDs in my home system. It was that good.

Wow Trevor, quite a battle. This project would have ended with me practicing my shot putting skills! LOL

Another chnange all the capacitor video gerry-rig all the semiconductor because you can't get the orginal parts