Yamaha CR-400 Repair

[@eatshitgoogle]

This is the kind of receiver I love the most. Brushed silver metal, wood cabinet and a simple design. What a beauty! It's hard to explain, but these smaller, simpler receivers have a unique charm to them.

[@Poppinwheeeeellllllieeeeez]

i love them. yamaha and sansui and even sony baby amps. I sold a sx-450 because of the dodgy tuner. the others are dead on.

[@geirendre]

I'm not totally on board with the Fuse/Voltage idea. As I see it, the fuse has a fixed internal resistance, and Ohm law applies to the fuse just as it does to any other component. So the voltage accross the fuse is given by the internal resistance of the fuse and the current passing trough it. You can also see the fuse as one resistor in a voltage divider, and the circuit it protects as the other resistor. The internal resistance of the fuse will probably change as it heats up from increasing current trough it (wattage dissipated accross it).

[@Waltkat]

Amazed at how clean the inside of that receiver is, considering it's age. Always loved these older Yamahas.

[@andybonneau9209]

I always understood the voltage rating on fuses was to prevent arcing across the fuse during over current event. Wire and fuses don't care about voltage, just current. Insulation and air gaps are for handling voltage, right?

[@len9518]

Your background noises are not a problem, No issue at all.

[@zopilotesky3014]

The speaker protect fuse is interesting. Brilliant in its simplicity. Thanks for sharing...

[@frankgeeraerts6243]

Very experienced and gentle diagnosis Tony !..............Allways or often surprised by the sound of these lower powered amps............thank you For sharing Tony ...

[@Obsfucation]

I agree with Geir Jenssen: the voltage rating on a fuse determines what the fuse can safely handle when it blows. That's why, as you pointed out, automotive fuses are rated for 32V but, that's because the fuse only has to prevent arcing after it blows with ~13.6VDC. It has nothing to do with the voltage in the protected path while it's not blown. The only "voltage" that's relevant when it's not blown is what develops due to the resistance and the current flow through the fuse; i.e., Ohm's law. Your statement that the fuse "at lower voltages these will go a lot higher in current.." is entirely incorrect. Even a cursory google search of "voltage rating of fuse" will explain this and so, no, a fuse shouldn't be rated for wattage. That's total nonsense.

[@johnb5519]

I used to watch you on my smart T.V. and was never allowed to comment on there. So now I'm subbed, and really enjoy your videos. I'm an old electrician, and always wanted to learn more about electronics, and this is the right place to come for that. Really like all the videos.

[@BobWilson84]

Great work and a nice quick fix!! I love working on Yamaha equipment, they seem to be built with serviceability in mind. One of the bigger receivers in this line has a hinged tuner section so you can work on bits without huge headaches. I’ve been looking for a resettable fuse replacement for testing purposes. Prices for 250v fuses has skyrocketed! Hope you have have a great holiday season Tony!

[@Poppinwheeeeellllllieeeeez]

I wish it was the 200. I have one sitting on my bench needing love. I was trying to save it after a previous repair attempt. did a full tear down detail, cleaned the pots and switches and gass, scrubbed the face plate. it looked new and ran beautifully. I recapped it and reflowed the joints. i decided to bias it before putting the lid on it. moved the VR slightly and a driver transistor blew clean in half. like a mini gunshot. the transistor was under rated as I found out from experts on AK. the previous owner swapped in bogus transistors. I found out the hard way and it has sat since. looking amazing as a boat anchor. LOL first one I blew up.

[@ElektrikaCo]

Would you be able to find a replacement for those driver transistors?

[@Poppinwheeeeellllllieeeeez]

@@ElektrikaCo yes. I can get them, but I was so disappointed I decided to give it some time and regroup in the New Year. I even tripple cleaned the glass and face plate. It was operating quite well, I was just being through.

[@xray111xxx]

I love the classics. The shorted fuses sound the best on them. Just kidding. I grew up on the good times when a receiver was cool and performed. Not the new AVRs like today. Love the old Pioneer, Yamaha, Kenwood, Sansui, Technics. And many more. You worked on allot my favorites Tony. The Pioneer SX series you did are my favorites. I sold some of the SX family as a kid sales person. I sold allot of Haman Kardon too. So much fun. Love everything you do Tony. My friends watch you too. You and Mr. Carlson's Lab are my favorites. You are thoughtful and careful. The surprises are just part of the fun. Google is great, but, nothing replaces proper training. I learn allot from watching you, and I have been around AV over 50 years. Keep up the great work. And Happy Holidays to you and your family.

[@adaboy4z]

Thanks for the bonus bulb fix. I fixed that same bulb on my CR-600!!

[@johnnytoobad7785]

at 04:00 Looks to me like 6.5mv (.0065) and 4.5mv (.0045), Well within any bias limit. Since you were on the DC-Volts scale.

[@unclebilly4696]

Correct, I saw the same thing.

[@keybutnolock]

Nice one, your years of experience show. Thanks for sharing.

[@TrevorsBench]

Odd fusing scheme in the power supply. The positive rail is fused but the negative is not? I'm guessing they are relying on the 500mA fuse on the center tap to be the protection. I guess it works because we witnessed a sick cap shutting it down.

[@EsotericArctos]

That's not really an odd fusing scheme. It was explained quite badly, but the fusing actually makes sense.

[@kennethiman2691]

I own or have owned about 50 receivers. Yamaha has some of the cleanest natural sound around. I have an 820 I need to go over soon.

[@jcampbell2481]

Yes I have a Yamaha R-302 and it produces very clean sounds. I was fortunate as I picked it up for free.

[@jcampbell2481]

Speaking of Yamaha receivers, does anyone know where I can buy a schematic for my Yamaha R-302?

[@buildstoys]

Nice to see another video Tony!

[@mdzacharias]

I have seen similar designs on other units, where the 10 ohm resistor (in this case) actually is the ground for the inputs and pre out. I've seen it on Hafler (.5 ohm and 1 ohm) Adcom (100 ohm) etc. Best as I can tell it's purpose is to suppress ground loop currents. In those designs however the open resistor causes an offset.

[@EsotericArctos]

A fuse that is older will sometimes, maybe even often blow below it reaches the specified rating. These would be a gentle, non-explosive type fuse failure and often is rectified just replacing the fuse. Sure, sometimes there will be an issue, but sometimes it is just the fuse is old. A violent failure is, of course, a different thing altogether. As others have mentioned, your whole theory on fuses is actually completely wrong compared to how they actually work in real life.

[@philipslighting8240]

Good Job Tony. Take care.⚡

[@HappyAccidentVideos]

I just got one on Facebook marketplace. Started to smell fire. I looked through the grill and saw the resistor was glowing red. Scared the crap outta me and stunk up my house

[@shadowboxer8638]

Polytome was an x-ray machine that did tomography. Saw one in Youngstown during radiology residency. Always needed an engineer to keep it working. Lol

[@geoffreykeane4072]

Great video Tony. I’m glad there was a problem 😊

[@fullwaverecked]

Good looking puppy you've got there. Nice score. Cheers!

[@marka1986]

Would it be possible to to highlight the pointer or continue to point with a pencil when tracing the schematics on the computer screen? I have low vision and it's difficult to see where the pointer goes sometimes. If it's is a big deal, don't worry about it. I realize it's frustrating no matter what you do someone wants it different. I appreciate your in depth detail on your repairs. I uesd to repair consumer electronics and now just once in awhile.

[@ElektrikaCo]

I ran across this channel relatively recently and now I can't stop binge watching :) Do you have a video where you touch on the theory behind capacitor reforming? Also, would you consider full recap a good preventative maintenance or waste of time and money if you plan on keeping the unit?

[@davidwhite9751]

Great video, thanks. I have a CR-400 and am busy replacing the meter and dial bulbs with LEDS. The existing bulbs are connected to an AC supply ( tags A5/A6) on the main board. The LEDs require a DC supply. What did you connect the LEDs to? Update: I strung the 3 meter LEDs and the dial LED, together with a 33 ohm current limiting resistor, all in series, and connected them across A6 (0V), and the +12V pin at the front rhs of the main pcb. Be advised that this circuit is soft-start and takes a couple of seconds to power on.

[@geirendre]

I like to run the unit for a while and then check it with an IR camera to see if any capacitor is getting warm. Sometimes that reveales a hidden issue that i otherwise would have missed.

[@RGD-Audio-Repairs]

Damn you are brave :) Id never connect speakers to 65mV outputs... I have a rule of thumb, of 50mV absolute max... in my opinion, No fully functioning amp should put out 50mV DC, So if there is more than 50, i wont connect speakers, and will assume a fault...

[@philipslighting8240]

Not true.

[@RGD-Audio-Repairs]

@@philipslighting8240 true or not... That is my general rule of thumb.. ive never seen a fully functioning, good health amplifier, put out 50mV DC, or higher.. Heck, When repairing my Peavey power amp, with shorted T03 transistors, it didnt even give out 50mV DC... Now repaired, it measures at 0.5 - 1mV DC at the speaker terminals, With the crowbar speaker protection triac's removed..

[@johnloupis2347]

I have a Technics SA 400 from the late 70's that puts out 55 and 61mv. I say it's to high but my tech says that's fine. There is no adjusting it. What would be the most likely cause of a high reading in this situation?

[@philipslighting8240]

@@johnloupis2347 I would not worry if its designed to be that way.

[@johnloupis2347]

@@philipslighting8240 Why would it be designed that way? What possible good could come from having DC voltage on the speaker terminals?

[@aarondavis8398]

I am currently working on one myself great 👍

[@zulumax1]

Less heat is created with high voltage and low current for a given wattage in a conductor. P= I * V , so low voltage and high current would expire the fuse with less watts. Would be a good video experiment to see how much difference there is.

[@johnyasuda6037]

Just wondering Tony, did you clean up the poor soldering on those output transistors? I am a detail person and you did not say or show that you fixed up that area. Otherwise, great job as always.

[@gbowne1]

Polytome tomography iirc, is basically looking for bone cancer. I've only heard it described a few times.

[@TheTrueVoiceOfReason]

Phillips Polytome tomograph? I know I've seen it in one of those old B movies, but can't quite place it. Was it a Vincent Price movie? Had to have been latter 50's, early 60's, most likely black and white film.

[@M-P-X]

Interesting simple DC offset circuit, next video? 🙂

[@geirendre]

But how can high ESR in a capacitor blow a fuse? It's just a resistance in SERIES with the capacitor. Wouldn't it be caused by a leaky capacitor (leaking DC current) like it had a resistor in PARALLEL across it (High EPR)? Well, I guess it depends.... on the circuit it's in.

[@iceberg789]

what is the point of putting a dual supply amp in a radio receiver anyways.

[@rustyrobinson8027]

Thanks again

[@aathiworld]

Hi , can you please advise me how to remove the Yamaha tuner knob ? Is it just pull out !

[@ivan1pipo]

you need to unscrew the screw that is inside, between the front panel and the sheet

[@Ultrafrozen]

Dad still runs his CR-400 in his shop.

[@radio-ged4626]

Found this info on the web "Polytome is a trademark name for a machine that can achieve multi-dimensional motion". So my guess is it's probably a medical scanner of some sort?

[@jimomertz]

What makes it natural sound? Some marketing BS? Surely you wouldn’t buy the unnatural sound model.

[@xraytonyb]

To me, all sound is unnatural, unless you are listening in real time to the original source. It's just that some unnatural sound sounds closer to the natural than others ;)

[@jimomertz]

@@xraytonyb Now that sounds like BS to me 🙂

[@garyedwards9617]

The loudness switch is what makes a natural sound Low listening levels would become more natural with this engaged Back in the day loudness switches were just boomy This switch would use the Harmon curve for low listening levels I owned one back in the day ;)

[@adaboy4z]

From my understanding Yamaha tested their equipment in a natural environment like a living room bedroom instead of a lab, hence the name natural sound.

[@johnsmith1474]

I hate it when guys stop to apologize for noise, it's more annoying than the noise.

[@xraytonyb]

I'm sorry for that. I guess the same could be said for those who complain when someone apologizes ;)