Pityocamptes
Member
Last Activity: 01-10-2025, 06:14 PM
Joined: 01-01-2025
Location: Phone, AZ
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Thanks. I will probe those with a dvm with the leads you indicated. No, I never got the other channel working again after i replaced all the caps. So yes, 2 gremlins, though I did prefer the Pinto... lol. Thanks again. -
Ok let me re-run those values with the VM tool on oscope I got. I will post the values on what you indicate above. ThxLeave a comment:
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To measure from B to E, I put the oscope ground on B and probe tip to E. Is that not correct? Thanks...Leave a comment:
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Ok so where do I need to start, and do I use the scope or a DVM? Thank you.Leave a comment:
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Here are pics of the Transistors between B to E.Leave a comment:
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I now I f''d up replacing all the caps at once. The funky black caps says 1068-7336 / 1470494-28 / 200uf 10v cap has + and - markings. I received my oscope and have these readings, I dont know if they help or if you can help me where to start. Thanks again.
oscope set on AC, 10x, 100ms
147 - sine wave 1.31v
135 - sine wave 1.8v
149 - half sine .12v
137 - half since .24v
coll Q41a - .01v no apparent wave
coll Q41b - .05v no apparent wave
coll Q42a - .07v no apparent wave
base Q42a - .05v no apparent wave
...Leave a comment:
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Q41a -
E 1
B 7
C 0
Q41b -
E .9
B 6.9
C 0...Leave a comment:
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So I have been going through the power circuit, waiting to get an oscope tomorrow, using my DVM at the moment. Anyways on the attached image I isolated the power supply and I do have approx 32 volts at pad 1. I tested the circuit to pad 2 and before R42 resistor I have 32v, after the 680k resistor I have approx. 14 volts. It appears that this also feeds the other channel circuit as well. Is this an issue, am I doing something wrong? Thanks
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Would something like this help me? [url]https://www.amazon.com/Oscilloscope-Generator-Transistor-Bandwidth-Transistors/dp/B0C8D6VJ1L/ref=sr_1_10?crid=N1O8BTYRWG9C&dib=eyJ2IjoiMSJ9.XO8KOWRK6UtrRFlERIMd8YhILTz4MKooZC_eRLr84OFgLit8DaIbHug0Rgq5-3SgCH2qOa0kgnrn290w0gv1uWKuRL2DqR8lZtu6Wo3l0qUZxfH-gB-5LVsC4YDMJLz4Rm7h1aGoF9egUYRtFVnhUWL7TPriChvjgayUKa8nXoxreCZp-qOdgFQLvZPXFmRLgBRW6Z61kxDMmjHztV0jQgpUmelOZVZ-59MpxMa1KaZxf3Vc0zkeiaDL6XWElNYOmF-dJ8WKJIKlTA2hFukbdGpWxlVzCCkmjzCLC46jpjM6Qe-bUTeXKm9rmPX8y8Wbg9zih7xr-btcnC8cE7TzTn11Luvc-U_yYMV2uINnhAc.Hn8_V_X8uwupm8KbmfEdvBDNWnn1kFSqt7oo9yUBhO4&dib...Leave a comment:
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Yes, I failed at that, thought that exact thing but it was to late. I swapped out everything from mid way to the outputs and the one channel still worked. After swapping out the other half, starting at the red line in pic it stopped working. So would the 50 dollar oscope on amazon be ok to use? I believe it had a sig gen and operated at 500khz. So at this point should i be measuring voltage with a VM or go the route of the oscope? Been a long time since Ive used one, would need some help. Thanks....Leave a comment:
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Yes prior to it not working now, I did swap the caps and no change. I did replace the resistors for the r416, 417, r426, r425 while at the parts store. No difference....Leave a comment:
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Yes, I swapped the inputs and the channel that worked continued to work, and the one that did not, still did not. I also swapped speaker wires to eliminate a blown speaker, both sides worked on the functioning channel (which after the cap replacement nothing works... ) Thx...Leave a comment:
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Thank you for your help! I really appreciate it. At the advice of another forum and due to the system being 50 yo, i decided to replace all the caps on the amp. I went down to the electronics store and picked up the caps, they looked at them via pics and the schematic I took and gave me the correct ones. Now, some were at most 3uf off, the guy that was helping me said that the parts they carried were standard and some of the cap values I assume are no longer considered standard? Anyways, cleaned up everything, double and triple checked everything and soldered. Well the sad part is now the channel...Leave a comment:
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I have an oscope but it's in storage, been a while since used. Would something simple like this be better to diagnose over a VM?
3 in 1 Digital Oscilloscope Set Handheld 500khz Bandwidth LED Display Oscilloscope Transistor Tester Signal Generator for Office Home [url]https://a.co/d/79F0veQ[/url]
Thanks.https://I have an oscope but it's in...tor for OfficeLeave a comment:
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Thanks! Speakers have been removed from amp output terminals, just testing power at amp out. I did swap speakers with known good channel and both speakers worked perfect. I also swapped c416 and c417 and it made no difference. I'm at a loss. Right up to the 1000uf + caps pads every voltage is identical or within 5%. After the cap, is where the one failed channel has 0 output. You can still hear audio its just not amplified. So probably just raw input?Leave a comment:
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Need some help fixing vintage RCA amp
Its an RCA VTT301L turntable with 2 channel amp.
Instead of retyping everything and what I've done if you could please read it here:
[url]https://www.edaboard.com/threads/i-need-assistance-tracking-down-failed-component-on-old-rca-amplifier.413493/[/url]
I will upload the schematic here if that helps. Thxhttps://Its an RCA VTT301L turntable...3493/[/url]...
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