one channel is out

[Lotto]

its very faint but its not working i replaced both tubes still not working im a novice what else should i do>
pv15

[AnotherJohnson]

If you’re sure it’s the PV15, you might check the fuses (specifically F1 or F2).

From the manual:

Fuses
The PV15 has two power transformers each of which is protected by a fuse. These fuses (F1 and F2) are located on the main pc board near the transformers. There is also an ac mains fuse (F3) located in the ac mains inlet socket on the back of the unit. A fail- ure of any of these fuses is a symptom of a more serious problem, and a competent service technician should be consulted. In no event should a fuse be replaced with a value or type different than that originally supplied. Correct fuse values are:
If configured for 100 or 120V:
F1 3AG type 3/4 amp, slow blow
F2 3AG type 1/2 amp, fast blow
F3 5 x 20mm T800 (800 ma slow blow)

You can determine if it’s really the PV15 by trial and error.

Swap the interconnects to the amp, and if the problem moves, it’s in the PV 15 or the source. If it doesn’t move, it’s in the amp or the speakers.

[roberto]

Hola, as AnotherJohnson said, it might be another thing. Did you check the RCA cable? Sometime a bad cable could produce a bad channel. Or, from the turntable, CD player.

When you turn on the pre, are both filaments of the tubes lit?...just guessing a possible cause.

Fuses are for both channels protection. If a fuse fails, both channels will not work.

We need more info...is the bad channel totally dead? Is there any hissing noise?

[admin]

Also, if not totally dead, does the output change with the volume control?

As other mentioned, make sure it's not a connection issue first, swap the left and right channel outputs/inputs to confirm.

[AnotherJohnson]

Perhaps this is wrong, but according to the manual, F1 and F2 in the pv15 look to be channel dependent. If F3 blows, both channels go out.

[Lotto]

swapped cables no change

[admin]

Perhaps this is wrong, but according to the manual, F1 and F2 in the pv15 look to be channel dependent. If F3 blows, both channels go out.

I'm looking at the schematics. I'm probably reading this wrong but it looks like the fuses are part of the power supply circuit, not the analog left/right circuit. However, my capabilities of reading these schematics put me in the "I know what those symbols mean" but not necessarily into "I know what's going on."

[AnotherJohnson]

Perhaps this is wrong, but according to the manual, F1 and F2 in the pv15 look to be channel dependent. If F3 blows, both channels go out.

I'm looking at the schematics. I'm probably reading this wrong but it looks like the fuses are part of the power supply circuit, not the analog left/right circuit. However, my capabilities of reading these schematics put me in the "I know what those symbols mean" but not necessarily into "I know what's going on."

I haven’t looked at the schematic. I assumed the only reason for two transformers would be a dual mono config.

But it’s a moot point because the problem is not the pv15.

[AnotherJohnson]

swapped cables no change

If the problem stayed on the same side after the cable swap, it’s your amp or your speakers.

Swap your speaker wires. If it moves, it’s the amp. If it doesn’t move, it’s the speakers.

[admin]

swapped cables no change

Just to clarify.

When you swapped L/R output analogs (going to your amp), the other speaker went dead.

And

When you swapped L/R input analogs (coming from your source), the same speaker is dead.

Correct?

[Lotto]

okay just played around a bit more... the conrad johnson is connected to a dynakit 70
to clarify this problem even further ...when swapping the cables on the dynakit or on the conrad Both sides go out
when switched back the left channel is working but not the right
at no time does the sound swap a speaker.
i swapped out right speaker with another and that did not solve the problem.
i did not bother to try different cables thinking that if it was them - one side would work no matter what

[Lotto]

in addition i appreciate everyone who is trying to help immensely thank you thank you thank you

[admin]

Try new cables. I have no idea why you would lose both channels by simply changing the L/R interconnect with each other unless there is some kind of connection issue. Is it reproducible every time? Try gently wiggling the connectors while playing music, does it bring the sound back temporarily?

[Lotto]

it does not bring back the sound temporarily. it is reproductable every time will have to buy new cables and try again hopefully on monday.
question ...the only extra cables i have at home are turntable cables with grounds on each end can these be used to connect the dynakit to the conrad without using the ground wire or are these cables not a good idea

[AnotherJohnson]

If they’re RCA to RCA style interconnects, and not part of a tonearm DIN to RCA cable, they will work. Keep the ground clear (tape it if you’re not confident of safely dressing it).

But phono interconnects aren’t your best choice for this, so plan to get some new ones.

[roberto]

Ok, let's make a truth table.
1) only left channel works.
2) you swapped the left cable from the preamp output to the right input of the amplifier, and from the preamplifier right output to the input left of the amplifier. Only left channel is working.

Conclusion: You have a bad right channel in the power amplifier.

[roberto]

The RCA input right channel at the amplifier could be loose or could be with a faulty contact or a faulty solder joint. Usually the Stereo 70 is ensemble by the owner. It's a kit. And usually it fails with a lot of poor solder joints.

[Lotto]

if i switch the dynakit to mono shouldnt both sides work then? that is not the case either that what is confusing to me also

[AnotherJohnson]

As Roberto points out, the kit amps are always dependent on the build quality, particularly on the soldering skills of the builder.

As admin points out and Lotto confirms, jiggling the interconnects affects the problem.

Combining both ideas, this could be due to interconnect failure … but it could also be due to a bad solder joint at the back side of the RCA inputs to the amp.

No one has said this yet … but the elephant in the room is the amp. There are so many obstacles kit amps present to good sound, that it’s hard to know where to begin.

Change the interconnects and see it it solves the problem. If the connection is still intermittent and tied to interconnect flexing, the RCA input jacks on the amp are at least part of the problem.

[admin]

Ok, let's make a truth table.
1) only left channel works.
2) you swapped the left cable from the preamp output to the right input of the amplifier, and from the preamplifier right output to the input left of the amplifier. Only left channel is working.

Conclusion: You have a bad right channel in the power amplifier.

If Roberto's statements are true, you have an issue with the right channel on the amp (presuming it is not a defect in the speaker, which you can check by swapping L/R speaker cable at one end).

Next step would be to pull the amp out for close inspection.

if i switch the dynakit to mono shouldnt both sides work then? that is not the case either that what is confusing to me also

I'm not sure how the mono/stereo switch is integrated but there could be a fault further down the line of the bad channel so this would not necessarily eliminate an issue in the right channel circuitry.