Repair of 1967-69 Harman/Kardon Five-Twenty with blown amplifier - germanium to silicon conversion

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This came in with a smoked left channel. It uses germanium outputs, which aren't available in any reliable sense.
Here we go over converting it to silicon outputs - the mj21193 - which are overkill, but provide little chance of failure if the wires get shorted again.
at the end of the video I get confused, because the right channel has distortion, making me think my conversion wasn't good - However I remember that the placement of the amplifiers is as seen from the rear! so the distortion channel is the original - my conversion works better than original.

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16 сен 2024

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Комментарии : 64

@brianfletcher9774 3 года назад

You are not a pest. Your bonus footage is always awesome. You can thank Shango for turning me on to your videos.

@danmackintosh6325 3 года назад

Same here, was just about to comment and apologize that I've just seen the RCA resurrection video in recommended & have to dash over there and see that first. To quote Governator, I'll be back...

@danmackintosh6325 3 года назад

And with that, I return to watch more cool stuff.

@jtc1983tx 3 года назад

Ditto.

@sirsuse 11 месяцев назад

EXCELLENT VIDEO! Love how you converted the bad channel to silicon as well. Your troubleshooting is top notch. Also, I really like the looks of that receiver. ❤

@shango066 3 года назад

The instructions say to use the capacitor wizard to look for shorted transistors in circuit because it wouldn't see the Transformer

@rsattahip 3 года назад

I liked your speaker trick for capacitors. I started using it last year.

@andrewstewart8704 3 года назад

@@rsattahip So do I, Freaking genius idea! Shango, you may be able to filter your your speaker testing capacitors, but love the raw unfiltered blurted out diagnostic thoughts like faulty components are almost out to get you and die in a certain way just to throw you off typical diagnostic paths.

@ukrainehamradio 2 года назад

@@rsattahip What are you talking about?

@FluxCondenser 3 года назад

Great diagnosis and fix by someone who really knows their stuff. Really enjoyed watching you bring this back to life and all the valuable insights you provided. Well done.

@mjg263 2 года назад

Nice SI conversion. Now if that was my receiver I would absolutely opt for converting the other channel. When you pointed out the distortion / oscillation at clipping I thought you knew it was the old channel doing it, I didn’t realize until the very end that you thought it was the converted channel lol.

@998cooper 3 года назад

Great vid. Intuitive & highly skilled JP. I don't think I've seen a HK component without an issue recently. Must be the age.

@Seiskid 3 года назад

Good video. I enjoyed this. Especially the conversion to silicon.

@derofromdown-under2832 3 года назад

Great diagnosis and repair... WELL DONE!!! 10/10

@knifeswitch5973 2 года назад

LOVE the early blackface integrateds and receivers! Thanks man

@RGB06084 3 года назад

Great work JP! Thanks for what you do here!

@saarike 3 года назад

Really nice looking receiver/amplifier and nice repair! Thanks it was a pleasure.

@justsumguy2u 3 года назад

Awesome, love the diagnostics

@dirtydon8661 3 года назад

I love these audio videos!

@dougbrowning82 3 года назад

Hmm. A late 1960s receiver with no AM band. I didn't realize people gave up on AM that early.

@JordanPier 3 года назад

I have some early 60s tube gear that has no AM.

@richardbrobeck2384 3 года назад

I have exact same receiver I restored it back in 1987 and it still works today as it did then . That unit is rated at 35 watts RMS per channel I have the factory schematic some where among my stuff . when I got mine the right side was bad .

@richardbrobeck2384 3 года назад

I am glad I have a spare set of transistors for mine .

@tarstarkusz 3 года назад

I have a 1975 Harman Kardon 720 and it's a kick-ass machine. Weighs a damn ton. The left and right channel are each their own 45w amplifier. It's like there is 2 complete stereos in the machine.

@Columba_Kos 3 года назад

Hi Richard. I don't see how it is possible that this receiver could be rated at 35 watts RMS. I think that Jordan's assessment of 10 watts RMS per channel is more likely.

@mauanderuk 3 года назад

Great work and a rather nice receiver that will live on.

@RadioFixer 3 года назад

Great job fixing this unit 👍👏👏

@boybravo689 2 года назад

thumbs up done excelent video tutorial presentation trouble shooting procedure new subcriber from the philippines

@badscrew4023 3 года назад

It's cool when you can compare one channel to another :)

@ric8868 3 года назад

Only fixing one channel kind of disturbs my OCD. When I work on stereo equipment and replace capacitors or transistors, I always do it on both channels, unless I am using the exact replacement for the part. Am I the only one?

@NOWThatsRichy 3 года назад

Yes, I would say it's best to replace the equivalent components on both channels, especially on very old equipment like this where components could have gone out of spec.

@fredfabris7187 3 года назад

I hear ya, however sometimes customers budget limits stuff

@robertdavis5714 3 года назад

Power transistors replacement..........sounds familiar. Cannot believe that BIAS adjuster functioned, Someone spent a considerable amount of time cleaning that unit. Jordan, if all goes well will see you Saturday with Kenwood 9000G, other repair person needs to put back together and why I did not make our appointment last Saturday.

@rsattahip 3 года назад

Socketed transistors, that's cool.

@bigalsmallengines 3 года назад

Good video buddy! I watched it all but forgot to like. Cheers! 🍻

@danhorton6182 2 года назад

The OCD in me really would like to get that other channel converted.

@jamesplotkin4674 3 года назад

I saw a staple stuck into the carpet covering your work area. Be careful of "shrapnel" as it can scratch surfaces and coatings.

@chetpomeroy1399 3 года назад

Very interesting that it contains all discrete components. I would think that by 1969 stereos like these would a chip or two in them.

@JordanPier 3 года назад

You really didn't start to see integrated circuits as common place until the mid 1970s. You did see integrated circuits in the IF strips on tuners like the UA707 - but other than that everything was discrete until about 1975, when you started seeing Sanken and STK power packs.

@Justplast 3 года назад

This is a hot item A1 Pier :)

@ravioli9728 3 года назад

Thanks JP

@zx8401ztv 3 года назад

Shame the owner didnt want both channels converted, the other germainium channel is likely to fail as well :-( Short sighted customer.

@JordanPier 3 года назад

It's a money thing. Everyone seems to think in the now rather than for the future. I have a problem customer who did not want anything more than the bare minimum against my wishes. He didn't end up using the receiver until months after he picked it up. Has issues from sitting and needs work in all the areas mentioned previously when he left it for repair. Come to learn he was flipping it on eBay. Oh well

@robinsattahip2376 2 года назад

Are you sure RU-vid is not going to hit you with a copyright violation because that sine wave resembles someone's so-called intellectual property? Good video, Thanks

@zulumax1 3 года назад

Interesting how different technicians will take different paths and sequence of troubleshooting, I enjoyed watching. I used the ON semiconductor MJ21193G and MJ21194G devices on a Marantz 2275. The spec sheets on the MJ21195G and MJ21186G devices seemed to be the same. Do you think the 93 would have worked as well as the 95 in this device? Both being PNP, not sure what what the differences are. Thanks....

@SeanBZA 3 года назад

Both will work, they exceed the original part parameters by a long way, and will work there, as the requirements are not critical. Sometimes they are too good, and need to be damped down a little as they can oscillate, when the originals were struggling with gain dropping with frequency. That will need either small sub 100pf capacitors across base emitter, or a ferrite bead on the base lead, to stop oscillation. Originals might be substantially lower gain at 50kHz, but new are still strong at 30MHz.

@DishNetworkDealerNEO 3 года назад

You should also make sure the customer doesn’t have bad speakers, and uses actual terminals on the speaker wires, instead of shorting the output!

@JordanPier 3 года назад

That's why I only have a demonstration warranty. I lecture them about their wires and how to properly connect them. I will even properly terminate them for a fee. However the demonstration of the amp is the only warranty. If they take it home and blow it up again and they didn't bring in their speakers and wires for me to examine - it's all on them

@SDsailor7 3 года назад

How do you select what component to feature in the videos? Do you need permission from the owner of the component to feature the component or not? Thank you

@JordanPier 3 года назад

Customers agree that their set may be used for educational purposes at the time they leave it. Never had anyone say no

@JordanPier 3 года назад

I usually pick something that either isn't done much, or hasn't been thought of as far as repairs and service

@SDsailor7 3 года назад

@@JordanPier Oh I see. Well that makes sense. Thank you for replying back.