Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: DPetrini on June 11, 2023, 03:41:33 AM
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Hi all, any idea where to look for? Apparently all seems done right at First slight. Thanxs
PS Yellow film Is kapton insulating film as could not find the original insulator i might Lost
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Can we see the bottom of the PC board and the socket wiring?
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Sure, thanxs
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What is your resistance to ground on terminal 7? Does that red wire touch pins 8/9 on the tube socket? If it does, that will give you very low voltage on terminal 7.
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Hi Paul, do you want I Measure the resistance between 7 and 8 with tubes and power on or not? Better double check before making disasters. I trieds now with no power and no tubes and read 4Mohm and the value continue to increase.
About the cable, i haved distanced the Red cable. After the change still read same voltage(0.961VDC). I can locally order the 4 transistors and i might replace all 4 Just to be sure. Unless other indications from you. Thanxs
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Now it looks like pins 1 and 2 on that 9 pin socket shown are touching.
I would not replace the transistors, as an issue like this is the output of the C4S being pulled down below any voltage present on any pins of any of those transistors, so it's likely external to the C4S board. You can check this by rotating the board 180 degrees and reinstalling it, then see if the low voltage moves to another terminal or stays where it is.
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I settled the proximity detected by you. Swopped 180 and remeasured . No way both 7 and 14 have same Reading 0.973 and 0.975 on 14.
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I would reflow the solder joints on each MJE5731A.
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Ok Will do later today when back to home.
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Done It. Used the desoldering gun to make a clean work. Resoldered with my best ...Shining tin Yes.. all...no way ..still 0.9 etcetc.
What can i check else?
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Remove the wires from OA and OB, turn the amp on, then measure the voltages at OA and OB.
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Tubes in or out?
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It won't matter for this test.
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If you meant to measure from point8 and Oa and from point 8 to OB ,see picture, i have 2mV at start that goes to 0mV in few seconds.
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Measure voltage from amp ground to OA, and amp ground to OB.
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OA 13mV. OB 8mV. Before the final Reading the voltage fluttuante up to about 25mV
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What are IA and IB now?
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Both measure to iec ground are 468 vdc
No tubes in of course
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Something is very likely not well soldered on the PC board. Can you take it out and show us the bottom side in better detail?
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Sure. See enclosed. What about if i get off all components ,clean It and reinstall new batch of 4 transistors? I have received them today from local supply
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Are you using lead free solder?
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I think its a very old kester. I finished It and Will now use weller Just arrived a couple of drops of the weller were used on this pcb i think when i reflow the soldering yesterday
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A very hot iron and low dwell time works well for the boards, but not enough heat will lead to flux building up between the solder joint and what it's supposed to solder, and you can end up with weird issues like this that don't make a ton of sense. The exception is the LEDs, which have so little ability to dissipate heat that they solder very quickly.
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So what do you advise please?
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I would reflow every joint on that PC board other than the LEDs. What you have is not consistent with a transistor failure.
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I am cooked as well. Reflow all,still not working. What if i dismantle It almost completely and start from scratch? Will you accept order for a list of components or out of your scope and should buy them locally?thanxs and apologize for not being a good fellow that makes things right First Time.
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You can contact replacementparts(at)bottlehead(dot)com about getting a replacement PCB and parts for your Stereomour. Some 60/40 leaded solder and a soldering iron set to 800+F would probably help too. The old Kester should work well provided it's leaded (not silver bearing).
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Thanxs! The solder station Is decent at 65w. Ordered now 60/40 Classic lead no silver. I want to make It working this time. Will check continuity or resistance at each soldering parte. Sent mail to your ref mail to ask offer quote. Cheers
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Dont think Will finish this amp. From thursday last week ,when i wrote for replacement parts,nobody took care of me. Not what i expected, honestly
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I will have Eileen check in the spam folder. Our e-mail service isn't always the best at proper filtering.