Originally posted by Lord Lucan I may be wrong, but I'm surprised if the capacitor is bypassed when a high voltage external pack is used.
I'm going off of memory from what I read about the HV 20-35 years ago. Ok, the HVP-1 cannot be used with the standard 285. It can be used with the 283. I went back to the user manuals so the information floating around on the Internet is incorrect. The standard 285 can use the LVP-2 pack which uses D-cell batteries.
According to the manuals you need to have fresh AA or the NiCad pack in the 285HV installed when using the HVP-1 in order to use the sync circuits. From what I remembered reading was the HV goes directly to the tube, it could have meant the flash capacitor. The flash tube uses 330+/-30V so the 510V is stepped down. Note the recycle time on the 285HV using the HVP-1 is 1.25 to 1.50 seconds with the internal NiCad pack and depending on if the rechargeable HV battery is used or not. On the 283 the recycle time is 1-3 seconds using the external HVP-1 batteries.
Using NiCad batteries shortens the recycle time from 9 to 4-5 seconds (full power flash).
283 no. flash & recycleSpecs (sorry too lazy to crop to the relevant text):
285:
285HV:
note: the 285HV has a "finite" number of flashes when using the SB-4 AC adapter because it needs AA batteries or the NiCad pack to power the sync circuits.
I haven't been able to find the user manual for the HVP-1 which would probably give more detailed specs than from the 283 system marketing brochure (blue page).