[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
CDC Electronics Assembly
Hello everyone,
Following discussions with Yves and Slava, I have attached two pdf
drawings describing the assembly process. Note that these drawings are
not to scale.
Please provide feedback. Board design will proceed with the new EDAC
connector.
Regards,
Fernando
Fernando J. Barbosa wrote:
> Hello everyone,
>
> I have attached a pdf describing the edge card connector from EDAC.
> This is similar to the one Gerard suggested but in 0.156" contact
> spacing. The connector part number is 307-030-500-202, which is a 30
> contacts on dual row with a HV rating of 1800 V AC rms, Thermoplastic
> Polyester insulator and $3.05. I searched for similar connectors and
> Sullins also has a similar one rated at 1800 V DC but with a different
> insulator (PPS Ryton). However, the cost for the Sullins part is five
> times higher at ~$15. The EDAC connector is stocked at Newark.
>
> Now for the assembly details which are based on Slava's drawings.
> Slava, I would appreciate if you could email your drawings to those on
> this distribution list.
>
> The assembly attempts to minimize the cable length from the straw to
> the connector:
>
> 1. 24 RG-174 cables are prepared as follows:
> a. Strip both ends so that there is the center conductor for
> soldering, insulation of center conductor, braid and outer insulation.
> Each is about .125 long so there are steps (different diameters).
> b. On the straw side, prepare as is now planned with solder ball and
> conductive rubber. Maybe a heat shrink piece could be applied to
> secure the conductive rubber cylinder and cover the shield in one step.
> c. On the connector side, slide each of the 24 cables into a small
> copper plate (perhaps a bit less than .125 thick) with 24 holes and
> solder the shield braids at the exit of the holes. The shields will
> all be connected together to the shield HV and to 2 connector pins.
> Solder each of the 24 center conductors to the connector.
>
> 2. The connector has 24 pins connected as in 1.c above, the next 2
> adjacent pins connect to the copper plate to the shield HV, as in 1.c
> above. The next two pins are left unconnected and insulated or cut.
> the final 2 pins are soldered to a cable to attach to the endplate for
> grounding (ground on card is connected to endplate in this way.
>
> 3. The back side (soldered connections) is sealed with the proper
> viscosity sealer and with low out-gassing characteristics (no silicone
> here). The finished part forms the connector assembly.
>
> 4. Connect all the cables from all the cable assemblies to the straws
> and endplate (grounds).
>
> 5. Attach dummy boards with straps to the edge card connectors on each
> of the cable assemblies.
>
> 6. Position the gas plenum Plexiglass cover and feed all the straps
> through their respective holes on the Plexiglass cover. Slide this
> cover while pulling or straightening the straps until the cover
> touches the connectors. Attach the connectors with screws, washer and
> neoprene seal washer.
>
> 7. Rotate CDC so that connector side is at top.
>
> 8. Apply sealer (see 3 above) around each of the connectors/plexiglass
> holes.
>
> In this way, we only need a short distance between the straws and the
> gas plenum cover. This is not very elaborate but I can provide a
> drawing if necessary to better explain this technique. Please note
> that if one of the wires in the straws brakes and shorts tripping the
> HV, all the 24 channels in the group will be off. This is required
> because the shields are also at HV and the RG-174 is not rated for
> this level of HV. So, this is inherently safe.
>
> There will also be an aluminum plate or aluminized mylar cover over
> the whole gas plenum and grounded for shielding.
>
> Please provide feedback so we can finish the design of the HVB PCB.
> The HVB PCB will have the HV distribution network, the connections to
> the preamp card connector, grounding, etc. The preamp card, as in the
> FDC, is removable from the HVB.
>
> Regards,
> Fernando
CDC_Assembly2.pdf
CDC_Assembly1.pdf
begin:vcard
fn:Fernando J. Barbosa
n:Barbosa;Fernando J.
org:Jefferson Lab
adr:Suite #10, 12B3;;12000 Jefferson Ave.;Newport News;VA;23606;USA
tel;work:757-269-7433
version:2.1
end:vcard