[TenTec] Fragile Radios

[Dr. Gerald N. Johnson]

On Thu, 2007-09-13 at 23:06 -0400, Joe Roberts wrote:
> On a related note, I wonder whether early digital gear like Omni V ages 
> so well. Specifically, wondering about the electrolytic capacitors.
>
> Case in point: Picked up an Omni V and the potential was there but I 
> found it to be a rather hissy and spitty set. NOT pleasurable to listen 
> to. Too much high frequency garbage. Made my ears hurt.
> 
> Contrary to the "If it ain't broke" law, I decided to replace a few 
> strategic caps on the logic board with super low ESR motherboard caps 
> like Rubycon MCZ and Sanyo Oscon. Wow, spurious noise level went way down.
> 
> Emboldened by this result, I recapped the entire IF/AF board with 
> similar quality caps. WOW WOW WOW. The V is now super quiet and real 
> well behaved. The difference is NIGHT and DAY.
> 
> Two questions:
> 
> 1) Were really good electrolytic decoupling caps for digital available 
> in 1989?

Yes, but they cost 65 cents each, and the others that were used cost 5
cents each.
> 
> 2) Are the yellow IC caps Ten Tec used even on the same planet 
> quality-wise as 2007 low ESR, HF rated caps.

No.
> 
> I think not. I figure Ten Tec used good quality, but not exceptional, 
> 1989 commercial grade parts....and these are getting rather long in the 
> tooth to boot.

Many I've checked had a 10% power factor right out of the sack from the
local electronics store.
> 
> A rig like the Omni V is digital and needs good caps and the ones in the 
>   radio were probably not the greatest then and certainly aren't now. My 
> theory is that the marginal decoupling capacitors are part of the blame 
> for some of the noisy rigs out there.

I'll go along with that.
> 
> Reminds me a lot of recapping old boatanchor radios, which I did a lot 
> of. Yanking out some funky wax caps and putting in Orange Drop 715Ps 
> really brought these old radios to life.

Same  problem, except the miniature electrolytics age faster and started
out poorer though the failure mode for the miniature electrolytics is
developing a high series resistance, different from the black beauties
and their leakage.

> 
> Time files...maybe we should start thinking about some of the 80s rigs 
> in the same light. My experience is that putting new, fresh, & really 
> fancy capacitors in the Omni V vastly improved the radio, and I only hit 
> a few of the high spots with the replacements. Will probably do the 
> whole radio over time.

I've been quietly advocating that for some time. Much modern solid state
stuff costs too little to bother with replacing the capacitors, though
TenTec rigs hold their value a lot better than a boom box.
> 
> I can now say that if an Omni V is at all noisy, it is not working right.
> 
> When I was messing with vintage tube radios, I struggled with the idea 
> of keeping them original, but for radios I wanted to use, I  usually 
> went ahead and recapped because the performance gains were so high.
> 
> I am following the same logic here with, so far, very positive results.
> 
> Joe N5KAT
> 
> 
I agree.

73, Jerry, K0CQ