Pas 3 no bass with phono - Help!

I have a Dyna Pas 3 pre-amp, restored,  hooked up to a VTA St70 or a Dyna ST70 and it sounds fantastic with CD or tuner.
Now with a turntable it sounds good but no bass coming out at all. All tubes are still original.

I tried with a different Pre-amp hooked to the same system and the bass is 'normal'
So I am thinking something is wrong with the phono section in the Pas 3.

Maybe replace the tubes in the Pas 3?

Please help.
Thanks
Gin

What is done by "restored" ?
Changing to lower resistance volume control could do exactly this..

modifying the selector wrongly could also make the above ( since the RIAA configuration is part
of the selector )

.

The pas-3 was recapped only; everything else is still original.
Here is the pic before:

And here is the pic after:

Did the phono input work properly prior to recapping? Keep in mind that a MC pickup likes to see an input resistance in the lower ranges. If you run a MM cartridge with a numerically small resistive load it may sound bass shy.

that is one of the cleanest original PAS3's I have ever seen!
I noticed on your 'modded' photo, you seem to be a capacitor short on the right hand pots?...I only see one yellow axial.......or is that just my imagination......

.

Oh Oh, that is it!
No, I am not sure, will open it and take a look weekend.

You don't see anything unusual on the phono board? No?

BTW, the sound is great when playing through CDP or tuner.

Thanks for now.

hrudu90 wrote:Oh Oh, that is it!
No, I am not sure, will open it and take a look weekend.

You don't see anything unusual on the phono board? No?

BTW, the sound is great when playing through CDP or tuner.

Thanks for now.

well I know there need to be two capacitors there, so yes, that may just as well be it.
Phono preamps are more 'sensitive' for one of the better words, so you may get away with a missing capacitor with CD & tuner, but perhaps not a phono preamp.

I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

daveshel wrote:I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

dave, which components are the RIAA?
Do they need to be replaced as well, just like other caps?

Thank you


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Two questions: What phono cartridge are you using?

Is there anything else connected to the PAS when you are testing the phono, other than the tube amplifiers you mention?

GP49 wrote:Two questions:  What phono cartridge are you using?

Is there anything else connected to the PAS when you are testing the phono, other than the tube amplifiers you mention?

I am using the Audio-Technica AT95 and the Denon DL110.
The cd player and the Dyna FM tuner are connected to the PAS 3 as well.


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hrudu90 wrote:

daveshel wrote:I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

dave, which components are the RIAA?
Do they need to be replaced as well, just like other caps?

Thank you


~~~

I believe they are on the middle wafer of the selector switch.

Seldom do the RIAA components need replacing (unless you are changing the circuitry...the original provided for switching among RIAA phono, NAB tape and flat response), and if you do, you may find they're hard to get if you want to duplicate the stock PAS circuit because they are close-tolerance parts.  Any old garden variety parts will inevitably result in inaccurate RIAA.

The cartridges would seem to be a good match. Associated equipment you mention should not have any effect. What many times does roll off the bass on a PAS phono is a cassette deck or other line-level solid state equipment...this includes computer line stages...connected to the TAPE OUT.

Gin, are you still there?? what did you find? Dale

Dale, Someone over there at AK suggested to clean the switch and I did clean the switch and I really can hear some improvement! Not bad, but I am still thinking it could be much better than that for sure.The highs and mids are amazing. And some one else suggested to replace the noisy resistors and move RIAA caps to the board but it would be waaayyy over my head! So for now I just enjoy them the way they are.
So if you guys have any ideas, let me know.
Thank you for asking.
Here you go

Dynaco in the morning.
Gin