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Finished Recapping my receiver but...

An interesting observation - circuit diagram vs. manual

So here is an interesting observation. Going back to the factory service manual and going against the circuit diagram it appears that Pioneer may have made some errors. If you look at the circuit diagram it calls for:

GWR-122: C206: 10uF 50v
GWR-122: C207: 47uF 50v
GWR-122: C208: 47uF 50v
GWR-122: C209: 47uF 50v
GWR-122: C210: 47uF 50v
GWR-122: C215: 1000uF 35v
GWR-122: C218: 47uF 10v
GWR-122: C227: 10uF 50v

But the service manual in fact calls for these values:
GWR - 122 C206 100uf 50v 100M 50L
GWR - 122 C207 470uf 50v 470M 50L
GWR - 122 C208 470uf 50v 470M 50L
GWR - 122 C209 470uf 50v 470M 50L
GWR - 122 C210 470uf 50v 470M 50L
GWR - 122 C215 100uf 35v 102M 35L
GWR - 122 C218 470uf 10v 470M 10L
GWR - 122 C227 100uf 50v 100M 50L

Notice that the Pioneer factory part number in fact added an extra "0" to each of the cap values. Now I'm certain that when I pulled the old caps that I paid very close attention to the value of the caps so I'm sure the service manual is wrong.
 
No, the service manual is correct. The "0" at the end means there is no multiple as in the following examples:

100M 50L equals 10 uF/50 volt
101M 50L equals 100 uF/50 volt
102M 50L equals 1000 uF/50 volt

So, according to my service manual for the SX-3800 the values for GWR-122 would be as follows:

C206,C227: 10 uF 50V
C209,C210: 47 uF 50V
C217: 220 uF 16V
C202,C203: 220 uF 80V
C207,C208: 47 uF 50V
C213,C214: 470 uF 16V
C215: 1000 uF 35V
C216: 100 uF 25V
C218: 47 uF 10V
C219: 470 uF 6V
C223: 2.2 uF 50V (note the "2R2" number in the manual. The R indicates a decimal place)
 
Hmm okay that makes sense now. I looked and looked at my power supply yesterday to figure out if I out a wrong cap in it and so far everything is right. Not sure how after recap that an amplifier that was working goes to becoming completely haywire.
 
Stevescivic said:
pin 20 +47v = 54.8v
pin 18 -47v = -40.7v
pin 22 +32v = 39.9v
pin 23 -32v = -25.8v

pin 24 -21v = -15.1v
pin 25 -14v = -6.95v

pin 15 +12.8v = 18.75v
pin 17 +5.5v when tuner active, 0v when not, = 6.1v tuner active / 5.3v in aux mode
pin 17 is controlled by 12.8v or 0v on pin 16 when the AM or FM is selected by the function switches.
pin 16 12.8v or 0v = 18.2v tuner active / 5.80v in aux mode

pin 13 +21v protection power on/off sense voltage = 29.7v

The three parts on the control board that made the board look browned/corroded around the metal heatsink edges that contact the board on GWR-122 appears to be Q204/Q208/Q209
Click to expand...

I know why. Starting with the power supply.

Your capacitor post and statement about pioneer making "errors" puzzled me. This was AFTER mattsd provided you with a list that I double checked as correct. That check wasn't a GLANCE, it involved everything I would have done to generate a list. EXCEPT the laborious typing. Now I realize I would have had a real treat trying to parse your first capacitor list.

I should have had you read and post the power supply voltages before anything was done.

We have work to do in the power supply. And I do not have a lot of time this weekend. But I will get to it.
 
I based my capacitor list off what I thought was the proper decoding based on the pioneer service manual BUT luckily I used mattsd's list and matched my components with his during my cap replacement process. Today I reflowed all solder joints on the amplifier section and power supply boards as well as cleaned off all the flux residue using 99.95% anhydrous alcohol and a stiff short bristle brush. Now at least I can now say that if we do any further work that we can now confirm that all parts that are supposed to be conducting electricity is doing so with a good solid connection.
 
Bump. Wanting to power up unit but don't want to blow anything up. Boards look like they're done right so I am stumped :(
 
Stevescivic said:
Bump. Wanting to power up unit but don't want to blow anything up. Boards look like they're done right so I am stumped :(
Click to expand...

Just reminding myself that this is a SX-3800...

The brown stuff at the bases (the pc board end) of the metal heat sinks the transistors are attached to is assembly glue, and is not a problem - it is normal. If the board itself were discolored (it would be as apparent from the other side of the pc board) then we would be looking for why they got so hot.

Q204 and Q208 are funky transistors that do get hot, and if we order parts (we have a sunday night deadline for that) we will come up with a few better parts. The original Q204 and Q208 have very thick collector leads in the center in an attempt to conduct the heat AWAY from the transistor and to the board, (which they DID) but then Pioneer didn't make allowances to get RID of that heat and just connected that thick lead with itty bitty copper traces that trapped the heat....

Does Q209 have it's own heat sink?


So at this point, we have the correct replacement value capacitors in the correct places?

If so, now after the work you did, please repeat the voltage measurements you did before, in case they have changed, and we will go from there.

Additionally please measure these voltages:
the three voltages each at Q201, Q205 and Q209, (left to right bce) INSULATE YOUR PROBE TIP for when you slip :yikes:
the voltage at the banded end of D207

For your edification, Q201's voltage output (pin 20 +47v = 54.8v) is too high, and the internal D207 voltage is the master reference for the +47 volt power supply voltage AND the +12.8 power supply voltage. BOTH of which are too high...

Q205's voltage output (pin 18 -47v = -40.7v ) is supposed to be a mirror image of the voltage on pin 20 (+47), and it isn't. So there's a problem here too.

Q209's voltage is a supposedly direct reading of D207, so I suspect D207 is damaged or an incorrect part. We may NOT need to replace transistors. BUT we WILL end up waiting for D207 a 14 volt, 1/2 watt zener diode.

It will be advantageous to spend a few bucks more and upgrade the current transistors in the power supply with new at the same time - and eliminate any doubt about getting it working after the first problem of the D207 voltage is fixed. We COULD end up futzing around quite a bit, or just do it in one fell swoop. They will be mouser.com numbers.



Sorry it took so long to get back to you, with everything going on, including the blizzard, I had been running on very little sleep. Now I don't seem to be able to catch more than 6 or 7 hours even when I try to make up the deficit.. but my head is a bit clearer. so many things to do, so little time...
 
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lol MTF I have no idea why you would apologize for taking longer to provide a reply! You're doing ME the favor and in that I should expect nothing. If its anyone that should be apologizing it should be us noobs that pester those around us for information.

I will mess with the unit and get one of my service techs buddies to look at my power supply to VERIFY everything is done right. I'm 99.95% certain ALL my electrolytics were done properly (b/c I doubled checked my values when pulling them AND did one cap at a time).


But before saying more I will give the unit to him, let him probe away at both the power supply and power amplifier portion of the boards (since I've removed the heatsink and output transistors from the unit for now). He'll verify everything, give me a quick training session on how to better read circuit diagrams and then from there I'll then provide some update info and then we'll proceed further.

Thanks again!
 
Stevescivic said:
lol MTF I have no idea why you would apologize for taking longer to provide a reply! You're doing ME the favor and in that I should expect nothing. If its anyone that should be apologizing it should be us noobs that pester those around us for information.

I will mess with the unit and get one of my service techs buddies to look at my power supply to VERIFY everything is done right. I'm 99.95% certain ALL my electrolytics were done properly (b/c I doubled checked my values when pulling them AND did one cap at a time).


But before saying more I will give the unit to him, let him probe away at both the power supply and power amplifier portion of the boards (since I've removed the heatsink and output transistors from the unit for now). He'll verify everything, give me a quick training session on how to better read circuit diagrams and then from there I'll then provide some update info and then we'll proceed further.

Thanks again!
Click to expand...

Be sure to show him that last post of mine, it'll give him a quick jump start on the situation - and I do not believe your work is at fault, I think a few transistors are iffy and a zener diode is bad.

But having the power supply voltages correct IS the first step in any repair or adjustment.

The power amp section is very unreliable with the power supply voltages being so far off, especially in the offset adjust section. Thus NOTHING is to be trusted in that amp with those power supply voltages. How do I know - I learned the hard way.

Got plenty of pointers for the amp, but they're inappropriate for now.
 
Hey mark it is worth mentioning that I there Wa's one transistor on the ps board that did discolor the backside of the pcb (but discolored on the joints only). Recall in one of my early posts on the amp that I had to reflow the joints on the transistors? So clearly it must have had to endure some serious heat to make a solder joint weak.

I am dropping it off to him tomorrow so hopefully all will be good in the next few upcoming days/weeks.
 
So its been literally a month since I've provided an update on my recap project. Too busy to look at everything so a friend of mine is helping me work on this unit and it has been determined that two of the FETS on the board (don't have location IDs right now) are exhibiting odd measurements.

Mark the zener diode you spoke of before checked out OK but I'm hoping my friend (who is well versed in reading circuit diagrams) can help me get the power supply working properly.

He suggested replacing the 2 large power filter caps as a precautionary measure but I do recall you saying that since the caps are quite large that they typically don't dry out nearly as fast as the small electrolytics on the various boards.

Hoping that within the next 2 weeks I'll have the FETs I need and I can get this unit up and running.
 
Hi everyone, finally get a chance to chime in again to share what my friend has helped me do so far. Its been determined by him that four of regulation (I believe that is what he said) transistors on the power supply board of my SX-3800 is giving him some off readings (what they are I'm not sure of but he says they're definitely not working right) and has requested that I order 4 replacements.

I would buy them from Mouser but being up in Canada it doesn't make much sense to pay $20 to ship 4 transistors when I can buy them here locally for a few bucks.

The markings on the transistors that are bad are:
2SD313 (qty 3) and 2SB682 (qty 1)

Local electronics supply store can get these in a few days but the parts guys told me that they have slightly higher voltages and dissipation currents which I'm not sure will have any negative impact on the power supply.

The parts guy stated to me in an e-mail below.

NTE has the following subs which exceed the specs:
3 NTE152 (2SD313) $1.83 2 days delivery
1 NTE292 (2SB682) $2.34 2 days delivery

Mark, I know you also asked about the Zener diode and from what I was told by my friend its working fine. My next step before conducting anymore voltage measurements is to replace my bad transistors with the NTE parts listed above (permitted that the variance in the spec is okay). Hopefully then will my amplifier be working properly.

Mark I know you were quite involved in my repairs so I'm guessing you'll chime in again to give me the go-ahead on these sub-replacements?

Thanks,
 
NTE is bad news normally. You never truly know what you are getting due to re-labeling and re-packaging, etc. Go with a trusted name.
 
Hi overload, I am in Calgary Ab. Arrow electronics here is a distributor but want me to purchase a total of 6000 of these two transistors as a bulk purchase! I don't think I would need that many....

I just think that paying 20 for 2 bucks worth of parts is kinda silly but if I must then I guess I'll have no choice.

Thanks
 
You can do better than NTE I hope, these are common transistors, nothing special.

Local electronics supply store can get these in a few days but the parts guys told me that they have slightly higher voltages and dissipation currents which I'm not sure will have any negative impact on the power supply.
Click to expand...

Not a problem.

the d313 is a 60v 3 amp 30 watt 5mhz transistor
the b682 is a 100v 4 amp 30 watt 8 mhz transistor

The voltages for that circuit are about 65v in and 47v out and I doubt that it EVER delivers over an amp (one ampere) of current.

Thus either of the transistor (sets) below would work.


512-KSB596Y pnp to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62
512-KSD526Y npn to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62

512-KSA940 pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.62
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.66

another common part would be the tip31C(npn d313) and tip32c(pnp b682).
it MUST be the C tip31(2)C or possibly the tip31B
the c is 100v
the b is 80v
the a is 60v and is too low.
without a letter (tip31,tip32) is 40v. and also too low.
 
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I'm going to pre-emptively replace the two FETs on the power supply board too since my friend says that if the voltage regulator transistors are bad that those FETs that also run really hot will likely be problematic if not now then for sure in the future.

I should know by the weekend what I'll need to order.

Thanks,
 
Stevescivic said:
I'm going to pre-emptively replace the two FETs on the power supply board too since my friend says that if the voltage regulator transistors are bad that those FETs that also run really hot will likely be problematic if not now then for sure in the future.

I should know by the weekend what I'll need to order.

Thanks,
Click to expand...

A time machine....

they don't make those 50v jfets anymore.

I've often wondered if an EchoWars current source would fill the bill there.

if they are working, leave them be.
 
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