I have had a Topfield 5800 since Christmas. I have had to open it up and 
make some mods due to some minor issues. I would like to share my experience 
in case it may be useful to others. Be aware that such mods will invalidate 
your warranty.

The first problem was hard drive buzz. It seemed less when I held the top 
cover down, so I thought a bit of damping would help. After opening up the 
box, I tried rubber pads, etc. It didn't. The buzz actually came from the 
display PCB on the front panel. I stopped this by putting gaffer tape over 
the back of the PCB, and over on to the metal chassis at the bottom. Buzz 
removed.

I have my main TV in a different room from all the boxes (so that the output 
of all can be piped by RF all over the house), and first tried connecting 
the Toppy via a SCART. This was OK, but required a SCART switch next to the 
boxes. A manual switch is a pain, as you have to go to the other room to 
change it. I tried a IR controlled SCART switch, but for reasons best known 
to itself, this seemed to lose the RGB voltage on pin 16, so I only got 
composite. As the TV has component as well as SCART inputs, I thought I 
would switch using the TV controller. This meant running two quad screened 
leads (one for Toppy, one for DVD combo) to the TV, switching the Toppy to 
YUV out and feeding it to component in.

Video fine, but audio (10m optical lead) was very hit and miss. I am told 
that any bend in a TOS cable dramatically attenuates the signal. Options: 
buy a higher quality optical cable (pricey) or use coax. Chose coax. So I 
used the fourth screened wire and connected an RCA socket to the Toppy back 
panel, soldered to the TOS driver diode. This gives about 1.5v peak compared 
to about 0.5v from the DVD, but the TV accepts it fine. One is forced to 
wonder what use TOSlink is, and to wish it had never been invented. Coax is 
better, cheaper and more convenient.

Re RF out. I have a DVD combo (LG RC185) that has RF pass-through but does 
not *play* to RF out (why?), and the Toppy does not have RF pass-through 
from its tuners. You have to get quite inventive to get all outputs to RF. I 
use a RF amp and feed one output to Toppy ANT1 in. Tuner1 out to ANT2 in. 
Other RF from amp to DVD RF in. DVD component out and coax audio to main TV. 
DVD SCART out to Toppy SCART in. The Toppy modulates this to its RF out when 
switched to Aux in, so cannot watch Freeview at one location and DVD (on RF) 
in another. I also have a Sky box, but this has RF pass through, and its RF 
out goes to Toppy RF in. An attenuator (12dB) is required here for reasons I 
have yet to ascertain. So I can get the 5 terrestrial channels, DVD, Sky and 
Toppy all over the house, but only after quite a struggle.

When we had TV and VCR it was all quite simple. The current scene is a 
ghastly mess of SCART, Component, SVideo, Composite, DVI and HDMI, with 
analogue audio on SCART and TOS/Coax digital audio. I believe even HDMI is 
likely to be superseded. One day it might all get sorted, but commercial 
competition always seems to screw things up.