My SX 838 Decided On A Vacation(Problem) ;o)

[markthefixer]

I have already checked all the resistors around pin 13 and on the power supply board and all were within spec.I'll re-check them again though ....I diode checked across b,c,e in both directions on my meter and compared those to new transistors(I Know how to check transistors):thmbsp:...Q2 is getting nice and hot with that extra voltage it's seeing....:yes: No problem replacing Q2 and Q3 and I do have those!

I'll now have to order some WZ 130s,as I don't have any...What are it's replacements? Break time on the 838. About the only other thing I can do at this time,would be to check both Pin 13 wires to ground for shorts...

This 838 makes a wonderful doorstop...I have a time line on this one,then it goes on E Bay for parts! :wave:

512-1N5243B Fairchild 13 V, 0.5W Zener

any 13v 1/2 watt zener diode will do, the 1n5243 part is the important designation.

 

[stratdeluxer]

512-1N5243B Fairchild 13 V, 0.5W Zener

any 13v 1/2 watt zener diode will do, the 1n5243 part is the important designation.

Thanks Mark....I'll check whatever else I can on the power supply board and then get some parts ordered....Please don't get discouraged with me. ...I appreciate your help,but at the same time,it's rewarding to figure some things out myself(somethings I have)....I've learned alot already by working on my SX 939 and my 2 1010s...I Know enough about electronics(especially tube guitar amps)to get myself into trouble...I'm learning more and more about solid state.There's way more components to deal with in these old receivers! It has been challenging,fun and rewarding also...

I thoroughly have appreciated your help and the forum and it's members!Your knowledge and help on this forum is welcomed and without you,I'd have to send these receivers out for expensive repairs! I'll get back at ya once the parts arrive...Just keep me from burning up stuff on that power supply board in the meantime! Thanks again for all of the help you provide on this forum! I Love this forum!

 

[stratdeluxer]

Mark.....I had replaced D8 and D9 on my board recently with the WZ 320s in those spots....Is this causing any problems in the way of voltages? I Just figured the 320s would work,since I didn't have the 130s....I see how wrong I was!

I just checked and saw that I had a package of 1N5244B Diodes rated for 14v .5 watt....Can I use these in place of the WZ 130s? These were ordered for my 1010,but I didn't end up using any...These are pretty close to correct spec...

I see I do in fact also already have an un-opened package of 1N5243B Diodes....I'm golden,other than I need more 100 mfd 63v and 100v electrolytics...

 

[markthefixer]

Mark.....I had replaced D8 and D9 on my board recently with the WZ 320s in those spots....Is this causing any problems in the way of voltages? I Just figured the 320s would work,since I didn't have the 130s....I see how wrong I was!

I just checked and saw that I had a package of 1N5244B Diodes rated for 14v .5 watt....Can I use these in place of the WZ 130s? These were ordered for my 1010,but I didn't end up using any...These are pretty close to correct spec...

I see I do in fact also already have an un-opened package of 1N5243B Diodes....I'm golden,other than I need more 100 mfd 63v and 100v electrolytics...

re: 320's replacing 130's --- very bad.... I wish folks would check substitutions from recommendations FIRST. That tends to generate threads like those that inspired my avatar and signature line.

 

[stratdeluxer]

re: 320's replacing 130's --- very bad.... I wish folks would check substitutions from recommendations FIRST. That tends to generate threads like those that inspired my avatar and signature line.

You are our mentor Mark....We learn from you! :ntwrthy:

Ironically enough,I used the 320s.I didn't realize I had the 130s the entire time! My bad....Worst case scenario,the thing blows up and I chuck it in the garbage!

I hate to be beat and would really like to get it working....Then I can chuck it in the garbage! :thmbsp:

 

[stratdeluxer]

FIXED!

Replaced Q2 and Q3 on the power supply board.Also replaced 1 3k3 resistor and D8 and D9 with the correct WZ 130s...I had WZ 320s in those spots earlier..Also replaced the 1384 transistor on the protection board again,as I was getting some funky readings from that.

The 4 SR3AM and 1 1S1886 were replaced for good measure also..Radio Shack had the first 4 diodes..

I fired the 838 up but had both wires to Pin 13 on the power supply disconnected...My voltages were as follows...

Pin 7....... -47 volts
Pin 9........ -12.9 volts
Pin 13......... 33 volts
Pin 14....... 12.4 volts
Pin 21....... 7.35 volts

After that I first re-connected the protection circuit wire from Pin 13 and saw these same voltages...

I then re-connected the power amp wire from the power supply of pin 13 and still saw the correct voltages...Heard the protection relay click on in each case...

Plugged er in,working great again.Has been running cranked up now for over an hour!

Thanks again Mark! You are appreciated...I'm happy.Just hoping she stays up and running for awhile? I run fans behind all of my receivers....Every little bit helps!

 

[stormy]

Awesome and congratulations!!!! Are you ready to fix my 838?

 

[stratdeluxer]

Awesome and congratulations!!!! Are you ready to fix my 838?

Personally I'd say Mark is your better candidate,simply cause your's seems more like a problem child more than mine was...:thmbsp:

Maybe you could open your's up and take the voltage readings at the same pinouts that I shown on the power supply board?

Very time consuming also...It's nice when things work though!

 

[stratdeluxer]

This SX 838 has been on all day playing tapes and cds....So far working great...No static,both channels clean and even...Plenty of volume...Fingers crossed,but so far so good...The FM tuner board needs to be gone through,but save that for another day...Offset and bias are perfect on both channels still..Channel seperation is very nice with this receiver!

Hey Mark.....Thanks again!