Bottlehead Forum

Bottlehead Kits => Eros Tape => Topic started by: KevO on January 28, 2013, 09:56:37 AM

Title: Eros issue
Post by: KevO on January 28, 2013, 09:56:37 AM
I an finally plugged in the RTR to the Eros. RTR has tape path kit and has Orton extended response head direct to O/P jacks.

I need help.....

My experience is following xcortes almost exactly. Hum in both channels. The hum was horrible until I grounded the RTR to the Eros. Now at moderate gain it is apparent and increases with volume.

My SS active buffer has a remote power supply 2 feet away. Doubt it is that.

I do have a tiny hum from the tube section of my Modwright Transporter. Does not increase with gain. And I turned it off when testing Eros.

The RTR does not have a grounded power cord, but even when I disconnect it, hum. I grounded the RTR to the outlet, hum.

I was very careful building the Eros. All tests OK. My diagnostic knowledge at this point is depleted.....

Haven't played a tape. Next step was to run test tape and align head with o'scope, but want to eliminate hum first.

Title: Re: Eros issue
Post by: KevO on January 28, 2013, 10:25:43 AM

After posting, I hit the showers. A shower is amazing at awakeing the ol' brain.

I have not grounded the Eros to my Buffer. I can't until I add a ground to it.

I will use the Cary Preamp from the TV room and ground the Eros to it. That may do it....

I'll post my results.

Title: Re: Eros issue
Post by: KevO on February 11, 2013, 02:24:35 PM

So, I swapped preamplifiers. I made shorting plugs for the inputs. I have grounded the Eros to the ground post of the preamp. I plugged the Eros into a different outlet with a different power cord. I have 60hz hum.

 The preamp power supply is remote and 20inches away through 2 inches of maple.  What should I try next?


Title: Re: Eros issue
Post by: Grainger49 on February 11, 2013, 03:21:01 PM
Give the link below a read and follow the steps.  I assume this is your first use of the Eros Tape preamp, right?,1667.0.html
Title: Re: Eros issue
Post by: Doc B. on February 11, 2013, 05:27:36 PM
I'm not really following either. Have you shprted the inputs of the Eros and listened?
Title: Re: Eros issue
Post by: KevO on February 12, 2013, 08:35:41 AM

I have shorted the inputs and tested. It hums. Seems like 60hz. When I move my hands around the tubes, the volume changes a bit.

If the pitch changed, I would have a theremin!

I reviewed all connections when I thought I had some measurement issues. Paul gave my measurements an OK.

Happy to review all of them again.

Just want to get tape playing before starting BPree kit.....



Title: Re: Eros issue
Post by: Doc B. on February 12, 2013, 09:01:51 AM
Kinda sounds like the tubes are on the more susceptible to hum side of the equation than some since the level changes with your hand getting close to them. If it's a soft 60Hz it may take different tubes to get it more quiet. If it is buzzy then it might be something to do with the AC mains ground in your system. If you want to bring it by I would be happy to bench it and look it over for you. Putting it on a scope can be very useful as you can see the various noise components and get a better idea of the source of the noise.
Title: Re: Eros issue
Post by: KevO on February 12, 2013, 11:09:45 AM
Thanks Doc. I am 805 miles away, so...

I bought a scope, but do not really know how to use it. I was planning to use it for the head alignment on my technics.

I am in a bit over my head, but that's how one learns.

I appreciate you folks are teachers, along with being engineers. And I include Grainger and other forum participant. Thanks!

We students can be trying sometimes. Newbs!

I do notice a difference when touching the tube shields on the EF86. I reoriented the Eros 180 degrees and also noted a difference. So the EF86 are picking up EMI.

I will check the grounding on the tube shield and sockets on the EF86's. These are the KREG readings I was concerned about:

                     A Board         B Board       Goal
KREG             1.9v              1.69v           1v

PJ said it means the EF86 are strong and working well.

I made short shielded cables, about 20", so moving the gear away from other components is difficult.

I know this will get worked out. Thanks.


Title: Re: Eros issue
Post by: KevO on February 24, 2013, 08:19:30 AM
Thanks for all the help.

I tested every ground around the input jacks and EF86 tubes for continuity. Everything looked good and tested fine, then I had a failed test. The ground wire of the input jacks failed the 2nd round of tests.

The ground wires in 20U and 26U were low in the terminal strip loop and my soldering missed the wires. They only had a physical connection. Soldered properly and bad hum is gone.

Flow my solder, the technician said.