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Yamaha CR-1020 mods with CR-2020 service bulletin

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pht714

Active Member
Hello,

I've read many threads talking about service bulletin mods (three service bulletin mods per ak database actually) on the bigger brother CR-2020 but couldn't find threads talking about mods for the little brother CR-1020. Many claims they both share the same circuitry except the CR-2020 has better tone control, better Phonos and more wattage output ...etc.

So, if they both share the same circuitry, can I apply the same mods as CR-2020?

One more question is my CR-1020 tuner string is broken. Any recommend what type of material would do the job?
also, all lamps on the speaker metters, signal and tuner pointer are out. Any ideas what voltage, amp, bulb type are those lamps?

Greatly appreciate
Thanks.
 
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On the 1020 there is no need to change the two D234 transistors. The 22 ohm fusistors should be changed to 22 ohm 3 watt, the other two resistors are 10 ohm not 33 ohm, but should be changed to 3 watt. Lamps on the 1020 are 12 volt 65 mA T1-1/4 size, Dave (dgwojo) here can fix you up.
 
Hello Merrylander,
thanks for the reply and recommended.

Since I'm in for the mods, figure might as well do a recaps.
I'm only going to do the easy part. I don't recall what series of CR ... probably CR 2020 that you did the whole recap and said that sonically, you can't heard the different; therefore, I'm going to do only the below boards since it is easy to get to rather than the tone control boards.

here is my shopping list and what I recorded what's on the boards.
Power supply:
50v 1000uf x2
63v 220uf
63v 100uf

Power Amplifier (x2 for both channels):
50v 100uf
6.3v 220uf
80v 47uf
25v 10uf
16v 10uf

Speaker relay board (sit on top of power supply board):
35v 100uf
25v 47uf
35v 1000uf
25v 220uf x2
25v 100uf
25v 10uf
6.3v 47uf
25v 3.3uf
10v 100uf
16v 10uf
6.3v 47uf
10v 100uf
25v 3.3uf
16v 10uf x5
25v 4.7uf
25v 22uf
25v 47uf
16v 47uf
35v 100uf
25v 22uf
35v 10uf x3
16v 10uf
16v 100uf

One of the thread you recommended to change the two D234 to TIP31AG.

http://audiokarma.org/forums/showthread.php?t=229362

need I still do it?

Forgive my ignorance, what is the different of fusistors vs resistors?

anything else should I need to put on the list?
how about tuner string?


Thanks.
 
That was only for the 2020, the D234s are OK for what load the 1020 puts on them. Fusistors are allegedly a combination of fuse and resistor that have a bad habit of changing resistance value. PITA. If there is a craft shop nearby (Michael's) get some #6 bead string, works like a charm.
 
Bringing back this thread from a few months ago b/c it's applicable...

I just checked the two 22 ohm fusistors on one of my 1020s, and they're way out - 12 and 14 ohms. The 10 ohm on the top of the board was right on, as were the rest of the red resistors. Is it necessary to change the red ones? They all measured within spec. (I lifted each one for testing)

Even with the fusistors being rather out of spec, the receiver does work. The +25 and -25 V power supply measures just over 27v, maybe because the fusistors are below spec?

Wonder of wonders, it even still worked when I put it back together. :)

This receiver sends a pop through the speakers when turning off, that's why I opened it up to begin with. Can anyone guide me - is this a switch problem or do you think it will go away with replacing the fusistors with new resistors?

One more thing - some previous owner (not sure of the history on this one) replaced the power cord with a 3-prong, attaching the ground to the chassis. Is this good? bad? indifferent? Perhaps the source of snapping in the speaker when turning it off, or when switching on/off lights on the same circuit? He also did a bit of a mess job on the lights... I feel an LED conversion for this one...

Any thoughts appreciated.

(and if anyone is wondering why I'm posting on such a variety of Yamaha units, I'm trying to make one mouser order for all the parts!)
 
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Pop on power off would indicate that your outputs are above/below 0 volts. When the protection relay opens it actually grounds the output. If there was some DC potential on the outputs you are hearing it being bled to ground.
 
merrylander said:
Pop on power off would indicate that your outputs are above/below 0 volts. When the protection relay opens it actually grounds the output. If there was some DC potential on the outputs you are hearing it being bled to ground.
Click to expand...

Hmm. I adjusted the DC on this one, (using the test points on the amp boards) got them both to 10mv without too much difficulty - it still pops. Am I missing something else? Next guess would be a problem on the output boards - am I looking in the right direction?
 
Couple observations.

I would never put on a grounded cord and ground on gear that didn't come with it.

Using bead string #6, which is smaller and slicker than the OEM tuner string, I've found it often helps to put an extra wrap on the tuner shaft.

10mV is the idle current ( DC Bias). Not the same as DC offset which is why your speaker pops. Measure the voltage between the + and - of the L/R speaker outputs with the volume down and an unused input, just like when you check idle current.

If it's significantly off from 0mV, there's some work to be done, possibly matching complimentary components in the circuit. Rob could offer more educated advice on that. There's a sticky in VSS about "DC offset and you."
 
Ok - so I removed the ground connection of the 3 prong cord, didn't seem to make a difference on the popping. I do notice that if I turn it off slowly, big pop. Moving the switch faster results in smaller pops... which is why I thought it was the switch.

I've measured the speaker outputs (volume a 0, unused input), and I get around -5mv on the left (once it stabilized - it starts out much higher), the right is about -10mv. I also notice that I can affect the numbers by cooling some components on the output boards with compressed air.

If I cool the transistor with the aluminum heatsink located at the extreme bottom rear corner of the board, it seems to move the readings towards 0. The baby transistor that is pressed against the large metal heatsink also seems to have some effect on the readings when I cool it, bit it might just be that the one below is getting cooled along with it. It's most predictable on the left channel, I can cool for 0mv. The right channel only gets about halfway to 0mv and then the cooling stops having an effect.

So - just a guess, but funky transistors? I plan to leave those boards alone until I deal with the power board resistors first, and at least investigate the power switch itself.

Thanks again for the tips.
 
The transistor against the heatsink is there to control the bias and keep the ouptuts from going into thermal runaway. That transistor and one or two others is probably the bias circuit and sometimes they're out of spec or as I often say, "worn to a nub."

The temperature change is affecting the hFE (gain) of the transistor.

Your offsets are not bad at all.

FWIW, I always turn the speaker selector off before powering off or on so I never really notice if there's a thump or not with the older CR's.
 
Learning more with every post. Thanks! I've been through that DC offset sticky... but it's a fair bit of reading and I need to go through it again. If those offsets are decent, then I'll leave the output boards well enough alone, and maybe it's the switch after all. Too bad it doesn't look easy to get out though...

I also noticed some other butchery at the power cord hookup - I'm going to have to open the other 1020 (that works flawlessly, though haven't checked any numbers), and see what it's supposed to look like, and refer to the schematic as well. There is a diode or resister or something that looks like it's supposed to be screwed to something... and it's just hanging in the air. :eek:

If I can get rid of the pops without having to change a bunch of transistors or capacitors, I'd like to just swap the out-of-spec fusistors and call it a day for this one.

I'll get to that tomorrow - and will post with pics.
 
here's a pic of the power in area of my 1020... some smart guy has decided that he knew better than the builders, and left this screw undone... looks like it's supposed to be a resistor connecting the chassis to the common wire of the AC power plug. He'd also connected the 3 prong wires the wrong way around, so the hot was on what was intended to be the common side by Yamaha... I realize it is AC, but still.

So... removed the ground wire connection from the 3 wire power cord, switched hot/common around, connected the resistor back to the chassis... I feel better about it now, but it still pops. I really wish that switch was easier to get at...

20120212_164640.jpg
 
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merrylander said:
On the 1020 there is no need to change the two D234 transistors. The 22 ohm fusistors should be changed to 22 ohm 3 watt, the other two resistors are 10 ohm not 33 ohm, but should be changed to 3 watt. Lamps on the 1020 are 12 volt 65 mA T1-1/4 size, Dave (dgwojo) here can fix you up.
Click to expand...

An old, old thread I know, but this is where I got the idea, so maybe my answer can come from here as well :)

I'm just wondering; I changed the two 10ohm fusistors to new 3w (I think the old ones were 1.5). However, since then I've noticed the unit is getting much hotter. much quicker.

Does that seem reasonable? I replaced many caps as well, so wondering if something else is causing the heat. But they were done in two stages, and I don't remember the heat issue after re-capping the relay board.
 
merrylander said:
Pop on power off would indicate that your outputs are above/below 0 volts. When the protection relay opens it actually grounds the output. If there was some DC potential on the outputs you are hearing it being bled to ground.
Click to expand...

Pop on power off could also be caused by the burnt out lamps.I have one here that was popping up until I relamped it. Quiet as a mausoleum now.
 
avionic said:
Pop on power off could also be caused by the burnt out lamps.I have one here that was popping up until I relamped it. Quiet as a mausoleum now.
Click to expand...

That cleaned up when I changed bulbs too. I'm just worried about the heat. Might just be in my head too :)
 
Does any one have Mouser part numbers for replacing the red fusistors that merrylander talking about at the top of this page ? I know I'm asking a lot here. I'm so new at this I just don't want to make a big mistake on this awesome Yamaha cr1020. I am wanting to rebuild both the power supply board and the ? What do I want to say relay board and to make one order to Mouser . There are many choices at Mouser it seems .
 
Slickrambler said:
Does any one have Mouser part numbers for replacing the red fusistors that merrylander talking about at the top of this page ? I know I'm asking a lot here. I'm so new at this I just don't want to make a big mistake on this awesome Yamaha cr1020. I am wanting to rebuild both the power supply board and the ? What do I want to say relay board and to make one order to Mouser . There are many choices at Mouser it seems .
Click to expand...
What resistance values are you looking for ?
 
Avionic you are the man ! 10ohm 3watt and 22ohm 3 watt for the power supply board. to replace the red fusistors which have not been replaced on my unit. Waiting on a lighted magnifying glass so I can actually see what the hell I'm doing. Thanks again !
 
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