Hitachi 3D7 ,8 and CX-W800 v Metal Bias tapes

In 1988 I bought a 3D8 and had to return it back to Curry's for an under warranty repair and they couldn't fix it as it was shipped like it.
The fault was that it couldn't record on metal bias tape from new out the box.
Ffwd to a few years a go and I purchased a second hand one and one a guess what, same metal issue. The tapes were fine on the B&o and nakamichi decks, so knew it wasnt the tapes. Tried fully erasing them and demagging the heads, nope... same fault. I assumed Hitachi had a feature that was not supposed to be there.
So other week for £12.50 I dropped on a mint 3D7, the first one, and guess what, same issue... Whats the odds? Tried all above, even cleaning the selector switch and rec/pb switch... same issue, infact, it could penetrate deep enough to erase the previous recording.
Right, 4th time lucky in the form of the CX-W800, nay problem at all with any tapes for recording at all!! Best £50 I've spent ever, but I have two helpful tips here worth remembering.
1) If you get a fault where the volume controls do nothing but blare out even on min, well thats the wires to the graphic / vol board broken. Mine had a dead CD deck and I'd say with the force needed to separate the cabinets, it would be easy to break these wires.
2) Dead Cassette decks are the micro switches underneath dirty.

And the tweeters on the 800 are purely cosmetic hence the dual cone stereo speakers. Sweeter less harsh sound imho.

I'm a ex tv engineer so if you're not happy with electrics etc, don't take the back off or anything.

That is weird are you sure it said it could play metal tapes on the box?

Its not a suprise that these mid-tier and budget oriented 3D's (or most of them?) had no metal recording or official playback. Metal tapes were very expensive back in the days and normal or chrome were the two choices for most people. Metal tape was an audiophile product.

Metal tapes need a much higher bias current to have a decent recording. Since there are positions only for Normal and CrO2, its no fault that the heads cant erase metal tapes. If it had enough bias current for metal tapes, the chromes would just sound muddy when recorded.

Playback isn't problem though, but you'll probably get a noticeable treble boost with metal tape.

3D's always had a good price/performance ratio and as I believe, good bass for the price.

The black Hitachis of that era had very cheap tape decks. I would not bother trying to record on them. The late 70s and early 80s Hitachis were much better quality.

lots of radios wont record on metal tapes and no its no fault of the 3d7 as they were not designed to in the first place

I have an original box for this model, features printed on the box include 'Metal Compatible Deck'. That's all it says, there's no mention of Metal tape facility with any reference to Playback or Record mode.

Hope this helps.