connecting an ipod

[Yorkie]

Thanks all,
I remember why I didn't start working on this radio now. Does anyone have a service sheet for it? If I recall correctly, this one is tricky to find.

Regards

Rob

Presumably they didn't bother issuing a separate circuit as it's the same circuit and chassis as the VHF3DRG ('RG' signifying 'Radio Gram'), which runs to seven pages of servicing data in 'Radio Servicing'.

If so, the stereo input from any source including an I-pod is straightforward. A glance at the circuit shows that when S5A/B/C is switched to allow input from an external source, all the preceding stages (AM/FM front end, IF stages, are muted and out of circuit, so in effect, the radio simply becomes a stereo amplifier. I've ringed the input socket and S5, and as you'll see, the LH/RG inputs go to the grids of V4. Pin2 V4A being the input for the LH channel, pin 7 V4B being that of the input of the RH channel. The ground is the chassis, and since it's an AC only receiver, that is also the mains earth. The radio isn't putting anything into your I-pod - your I-pod is feeding audio to the grids of V4. No worries.

Hope that helps a bit Rob.

[Bushbaby]

Hi David,
Yes, it helps greatly. I just need to finish my Nordmende and then the work on VHF3d will commence.

Best Regards

Rob

[AlanBeckett]

I think it's a bit more complicated that that David. As far as I can tell 'RG' is indeed a (Mono) Rdiogram and has a Single Channel P-P Output stage. 'SG' on the other hand implies Stereogram, and has two Single-ended EL84 Output stages.
The VHF3D has the Stereo Output Stages, at least on the ones I've seen.

Alan

[pwdrive]

The 3DRG has ten valves being a mono set, the 3D and the 3DSG have nine valves, the extra valve in the 3DRG is the EABC80 for the AM det. and the FM discriminator, the triode section of that valve is the AF amp to drive the twin triode phase splitter for the push pull output stage.

Not sure of the difference between the 3D and the 3DSG, maybe the latter takes a stereo decoder?

Lawrence.

[Yorkie]

I think it's a bit more complicated that that David. As far as I can tell 'RG' is indeed a (Mono) Radiogram and has a Single Channel P-P Output stage. 'SG' on the other hand implies Stereogram, and has two Single-ended EL84 Output stages.
The VHF3D has the Stereo Output Stages, at least on the ones I've seen.

Alan

The circuit I showed is that of the VHF3DSG stereogram, which as you say, has two single ended EL84 output valves. The part of the circuit that I ringed was from the input socket to the two halves of the ECC83 twin triode (pre-amp) that feeds the LH/RH inputs to the EL84s. I assume that the circuit isn't dissimilar to the VHF3D radio and just tried to focus on the fact that the tuned stages and IF stages prior to the audio stage are of no concern, (and neither really are the EL84s) in focusing on Rob's query about connecting an I-pod.

If Rob pokes a signal into pin2 of the ECC83 it should come out of the LH speaker, and pin 7 of the ECC83 should come out of the RH speaker.

The point I was trying to get across was that if an I-pod is connected to the stereo input socket of the radio the I-pod won't come to any harm.

[AlanBeckett]

All I was pointing out is that the Book is not to be trusted, and neither are/were Pye when it came to jiggery-pokery with the Circuits.
For example, according to the Book the VHF2DSG has Solid State Diodes for the am Detector and Discriminator, plus a Balance Control - R27/28. It does say 'Early Models.
The VHF3DRG uses an EABC80 and being Mono doesn't have a Balance Control.
The VHF3DSG Diagram is very similar to the VHF2DSG but doesn't have a Balance Control whereas the VHF3D actually does - it's not very visible or accessible, but it's there.
So, although none of the above actually affects connecting a Stereo Source it's as well to be aware that there are differences if you're trying to repair one.

Alan

[Old Sparky]

If the radio is mono, it would probably be a good idea to include a resistor of some 4.7 - 10k in series with each channel, joining the 'remote ends of the resistors together and connecting this to the 'aux-in' point This is always done when wiring an 'aux-in' connection to a mono car radio in order to prevent a short circuit between the LH & RH channel outputs of the Ipod, MP3 player, etc.

[pwdrive]

Rob's radio is stereo audio (no FM stereo decoder), there are some pics in another thread on this forum (search..VHF3D)

But yes, if it's a mono feed that's required then summing resistors should be fitted.

Lawrence.

[Yorkie]

For the sake of clarification, Rob's query was about connecting the stereo output of his i-pad to the stereo input of his VHF3D radio.

Hopefully he's sorted now!